Cyber Trackr - MS Exchange 2010 Edge Transport Server STIG

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V-33556 Updated

Findings ID:	Exch-2-334	Rule ID:	SV-43976r1_rule	Severity:	medium	CCI:

Discussion

Email is only as secure as the recipient. When the recipient is an email server accepting inbound messages, authenticating the sender enables the receiver to better assess message quality and to validate the sending domain as authentic. One or more authentication techniques used in combination can be effective in reducing SPAM, PHISHING, and FORGERY attacks.

The Sender ID Framework (SIDF) receiver accesses specially formatted DNS records (SPF format) that contain the IP address of authorized sending servers for the sending domain that can be compared to data in the email message header. Receivers are able to validate the authenticity of the sending domain, helping to avoid receiving inbound messages from PHISHING or other SPAM domains.
~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-SenderIdConfig | Select Name, Identity, Enabled

If the value of 'Enabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderIdConfig -Enable $true

V-33557 Updated

Findings ID:	Exch-2-336	Rule ID:	SV-43977r12_rule	Severity:	medium	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to availability impacts.

Filters that govern inbound Email evaluation can significantly reduce SPAM, PHISHING, and SPOOFED Emails. Messages from blank senders, known SPAMMERS, or 0-day attack modifications must be enabled to be effective.

Failure to enable the filter will result in no action taken. This setting should always be enabled. ~~ECSC-1~~

Checks

This requirement is N/A for SIPR enclaves.

This requirement is N/A if the organization subscribes to EEMSG or other similar DoD enterprise protections for email services.

Open the Exchange Management Shell and enter the following command:

Get-SenderFilterConfig | Select Enabled

If the value of 'Enabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderfilterConfig -Enabled $true

V-33558 Updated

Findings ID:	Exch-2-339	Rule ID:	SV-43978r1_rule	Severity:	medium	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to availability impacts.

Filters that govern inbound Email evaluation can significantly reduce SPAM, PHISHING, and SPOOFED Emails. Messages from blank senders, known SPAMMERS, or 0-day attack modifications must be enabled to be effective.

Having items identified in the ‘allow’ list causes other SPAM evaluation steps to be bypassed, and therefore should be used only with an abundance of caution. If SPAMMERS were to learn of entries in the ‘allow list’ it could enable them to plan a denial of service attack (or other attack) by spoofing that source. ~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-IPAllowListConfig | fl

If the value for “Enabled” is set to “True” this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:
Set-IPAllowListConfig -Enabled $true

V-33560 Updated

Findings ID:	Exch-2-342	Rule ID:	SV-43980r1_rule	Severity:	medium	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to availability impacts.

Filters that govern inbound Email evaluation can significantly reduce SPAM, PHISHING, and SPOOFED Emails. Messages from blank senders, known SPAMMERS, or 0-day attack modifications must be enabled to be effective.

Having items identified in the ‘allow’ list causes other SPAM evaluation steps to be bypassed, and therefore should be used only with an abundance of caution. If SPAMMERS were to learn of entries in the ‘allow list’ it could enable them to plan a denial of service attack (or other attack) by spoofing that source.
~~ECSC-1~~

Checks

Access the EDSP and identify the SMTP ‘allow list’ settings.

Open the Exchange Management Shell and enter the following command:

Get-IPAllowListEntry | fl

If the result returns any values, this is a finding.
If the result returns any values, but has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and noting identifiers from above, enter the following command:

Remove-IPAllowListEntry -Identity <IP Allow List entry ID>

V-33561 Updated

Findings ID:	Exch-2-705	Rule ID:	SV-43981r3_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound message size. Failure to control the configuration strategy can result in loss of data or system availability.

This setting enables the administrator to control the maximum message size on receive connectors. Using connectors to control size limits may necessitate the need to apply message size limitations in multiple places, with the potential of introducing conflicts and impediments in the mail flow. Changing this setting at the connector overrides the global one. Therefore, if operational needs require it, the connector value may be set lower than that of the global value with the rationale and documented in the EDSP.~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message receive size and if signoff with risk acceptance is documented for the receive connector to have a different value.

Open the Exchange Management Shell and enter the following command:
Get-ReceiveConnector | Select Name, Identity, MaxMessageSize

or

Get-TransportConfig | Select Identity, MaxReceiveSize

Identify Internet-facing connectors on the Edge Transport server.

If 'MaxMessageSize' is set to a numeric value different from the global value, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of ‘MaxMessageSize' is not the same as the global value, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -MaxMessageSize <MaxReceiveSize>

If an alternate value is desired from the global value MaxReceiveSize, obtain signoff with risk acceptance and document in the EDSP.

V-33563 Updated

Findings ID:	Exch-2-708	Rule ID:	SV-43983r2_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous inbound connections allowed to the SMTP server.

By default, the number of simultaneous inbound connections is 5000. If a limit is set too low, the connections pool may get filled. If attackers perceive the limit is too low, they could deny service to the Simple Mail Transfer Protocol (SMTP) server by using a connection count that exceeds the limit set. By setting the default configuration to 5000, attackers would need many more connections to cause denial of service.~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the 'Maximum Inbound connections' value.

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, MaxInboundConnection

Identify Internet-facing connectors on the Edge Transport server.

If 'MaxInboundConnection' is set to a different numeric value or unlimited, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of 'MaxInboundConnection' is not set to 5000, this is a finding.

Fix

Noting the Internet-facing receive connector name, open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -MaxInboundConnection unlimited

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33565 No Change

Findings ID:	Exch-2-710	Rule ID:	SV-43985r1_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning. This configuration controls the number of idle minutes before the connection is dropped. It works in conjunction with the Maximum Inbound Connections Count setting.

Connections, once established, may incur delays in message transfer. If the timeout period is too long, there is risk that connections may be maintained for unnecessarily long time periods, preventing new connections from being established.
ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the 'Connection Timeout' value.

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, ConnectionTimeout

If the value of 'ConnectionTimeout' is set to 00:05:00, this is not a finding.

If 'ConnectionTimeout' is set to other than 00:05:00, and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -ConnectionTimeout 00:05:00 or other value as identified by the Email Domain Security Plan.

V-33566 No Change

Findings ID:	Exch-2-715	Rule ID:	SV-43986r1_rule	Severity:	medium	CCI:

Discussion

This control is used to limit the servers that may use this server as a relay. If a Simple Mail Transport Protocol (SMTP) sender does not have a direct connection to the Internet (for example, an application that produces reports to be emailed) then it will need to use an SMTP Receive Connector that does have a path to the Internet (for example, a local email server) as a relay.

SMTP relay functions must be protected so third parties are not able to hijack a relay service for their own purposes. Most commonly, hijacking of relays is done by SPAMMERS to disguise the source of their messages, and may also be used to cover the source of more destructive attacks.

Relays can be restricted in one of three ways; by blocking relays (restrict to a blank list of servers), by restricting use to lists of valid servers, or by restricting use to servers that can authenticate. Because authenticated connections are the most secure for SMTP Receive Connectors, it is recommended that relays allow only servers that can authenticate.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, PermissionGroups

If the value of 'PermissionGroups' is 'AnonymousUsers' for any non-internet connector, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -PermissionGroups and enter a valid value other than 'AnonymousUsers'.

V-33567 No Change

Findings ID:	Exch-2-718	Rule ID:	SV-43987r1_rule	Severity:	medium	CCI:

Discussion

The Simple Mail Transfer Protocol (SMTP) Receive Connector is used by Exchange to send and receive messages from server to server using SMTP protocol. This setting controls the encryption strength used for client connections to the SMTP Receive Connector. With this feature enabled, only clients capable of supporting secure communications will be able to send mail using this SMTP server. Where secure channels are required, encryption can also be selected.

The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from the client to the server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender.

Individually, channel security and encryption have been compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between the client and server.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, AuthMechanism

If the value of 'AuthMechanism' is not set to 'Tls', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -AuthMechanism 'Tls'

V-33568 No Change

Findings ID:	Exch-2-721	Rule ID:	SV-43988r1_rule	Severity:	medium	CCI:

Discussion

The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. There are several controls that work together to provide security between internal servers. This setting controls the authentication method used for communications between servers. With this feature enabled, messages can be securely passed from a partner domain securely.

The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from server to server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender.

Individually, channel security and encryption can be compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between servers.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, DomainSecureEnabled

If the value of 'DomainSecureEnabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -DomainSecureEnabled 'True'

V-33569 No Change

Findings ID:	Exch-2-724	Rule ID:	SV-43989r1_rule	Severity:	medium	CCI:

Discussion

Sending unencrypted email over the Internet increases the risk that messages can be intercepted or altered. Transport Layer Security (TLS) is designed to protect confidentiality and data integrity by encrypting email messages between servers and thereby reducing the risk of eavesdropping, interception, and alteration. This setting forces Exchange to offer TLS before using basic authentication.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector -Identity <'ServerUnderReview\ReceiveConnector'> | Select AuthMechanism

If the value of 'AuthMechanism' is not set to 'Tls, BasicAuth, BasicAuthRequireTLS', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -AuthMechanism 'Tls, BasicAuth, BasicAuthRequireTLS'

V-33572 Updated

Findings ID:	Exch-2-727	Rule ID:	SV-43992r2_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations.

This configuration controls the maximum number of recipients who will receive a copy of a message at one time. This tunable value is related to throughput capacity and can enable the ability to optimize message delivery.

Note: There are two types of default Receive Connecters:
Client Servername: This Receive connector accepts SMTP connections from all non-MAPI clients, such as POP and IMAP. As POP and IMAP are not authorized for use in DoD, these should not be present. Their default value for MaxRecipientsPerMessage is 200.
Default Servername: This Receive connector accepts connections from other Hub Transport servers and any Edge Transport servers. Their default value for MaxRecipientsPerMessage is 5000.~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the 'Maximum Recipients per Message' value:

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, MaxRecipientsPerMessage

For each receive connector, evaluate the 'MaxRecipientsPerMessage' value.

If the value of 'Maximum Recipients per Message' is set to a value other than 5000, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of 'MaxRecipientsPerMessage' is not set to 5000, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -MaxRecipientsPerMessage 5000 or other value as identified by the EDSP.

V-33574 No Change

Findings ID:	Exch-2-730	Rule ID:	SV-43994r1_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound message size. Failure to control the configuration strategy can result in loss of data or system availability.

This setting enables the administrator to enable ‘chunking’ on received messages as they arrive at the domain. This is done so that large message bodies can be relayed by the remote sender to the receive connector in multiple, smaller chunks.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, ChunkingEnabled

If the value of 'ChunkingEnabled' is set to 'True', this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -ChunkingEnabled $true

V-33575 No Change

Findings ID:	Exch-2-733	Rule ID:	SV-43995r1_rule	Severity:	low	CCI:

Discussion

For receive connectors, unclear naming as to direction and purpose increases risk that messages may not flow as intended, troubleshooting efforts may be impaired, or incorrect assumptions may be made about the completeness of the configuration.

Collectively, connectors should account for all connections required for the overall email topology design. Simple Mail Transfer Protocol (SMTP) connectors, when listed, must name purpose and direction clearly, and their counterparts on servers to which they connect should be recognizable as their partners.
ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity

Review the naming for connectors. If the connectors are not clearly named for purpose and direction, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Name <'NewName'> -Identity <'ReceiveConnector'>

V-33576 Updated

Findings ID:	Exch-2-736	Rule ID:	SV-43996r2_rule	Severity:	medium	CCI:

Discussion

Attackers can use automated messages to determine whether a user account is active, in the office, traveling, and so on. An attacker might use this information to conduct future attacks. Ensure Automatic Forwards to remote domains are disabled, except for enterprise mail that must be restricted to forward-only to .mil and .gov. domains.

Before enabling this setting first configure a remote domain. ~~ECSC-1~~

Checks

Non- Enterprise Mail Check Content:

Open the Exchange Management Shell and enter the following command:

Get-RemoteDomain | select identity, AutoForwardEnabled

If the value of 'AutoForwardEnabled' is not set to 'False', this is a finding.

Enterprise Mail Check Content:

If the value of 'AutoForwardEnabled' is set to 'True', this is not a finding.

and

In the Exchange Management Shell and enter the following command:

Get-RemoteDomain

If the value of 'RemoteDomain ' is not set to a ' .mil' and/or '.gov ' domain(s), this is a finding.

Fix

Non- Enterprise Mail Fix Text:

Open the Exchange Management Shell and enter the following command:

Set-RemoteDomain -Identity <'RemoteDomainName'> -AutoForwardEnabled $false

Enterprise Mail Fix Text:

New-RemoteDomain -Name <Descriptive Name> -DomainName <SMTP address space>

Set-RemoteDomain -Identity <'RemoteDomainName'> -AutoForwardEnabled $true

V-33578 No Change

Findings ID:	Exch-2-739	Rule ID:	SV-43998r1_rule	Severity:	medium	CCI:

Discussion

Tarpitting is the practice of artificially delaying server responses for specific SMTP communication patterns that indicate high volumes of SPAM or other unwelcome messages. The intent of tarpitting is to slow down the communication process for SPAM batches so that the cost effectiveness of sending SPAM is reduced and directory harvest attacks may be thwarted.

A directory harvest attack is an attempt to collect valid email addresses from a particular organization so that the email addresses can be added to a spam database. A program can be written to collect email addresses that return a 'Recipient OK' SMTP response and discards all email addresses that return a 'User unknown' SMTP response.

Tarpitting makes directory harvest attacks too costly to automate efficiently.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, TarpitInterval

If the value of 'TarpitInterval' is not set to 00:00:05 or greater, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -TarpitInterval 00:00:05

V-33579 Updated

Findings ID:	Exch-2-741	Rule ID:	SV-43999r2_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. This setting controls the maximum number of hops (email servers traversed) a message may take as it travels to its destination. Part of the original Internet protocol implementation, the hop count limit prevents a message being passed in a routing loop indefinitely. Messages exceeding the maximum hop count are discarded undelivered.

Recent studies indicate that virtually all messages can be delivered in fewer than 60 hops. If the hop count is set too low, messages may expire before they reach their destinations. If set too high, an undeliverable message may cycle between servers, raising the risk of network congestion.
~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the value for 'Receive Connectors”.
Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select name, MaxHopCount

If the value of 'MaxHopCount' is set to 60 this is not a finding.

If the value of 'MaxHopCount' is set to a value other than 60 and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -MaxHopCount 60

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33581 No Change

Findings ID:	Exch-2-743	Rule ID:	SV-44001r1_rule	Severity:	medium	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to availability impacts.

Filters that govern inbound Email evaluation can significantly reduce SPAM, PHISHING, and SPOOFED Emails. Messages from blank senders, known SPAMMERS, or 0-day attack modifications must be enabled to be effective. ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-RecipientFilterConfig | Select Enabled

If the value of 'Enabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-RecipientFilterConfig -Enabled $true

V-33583 No Change

Findings ID:	Exch-2-751	Rule ID:	SV-44004r1_rule	Severity:	low	CCI:

Discussion

For send connectors, unclear naming as to direction and purpose increases risk that messages may not flow as intended, troubleshooting efforts may be impaired, or incorrect assumptions may be made about the completeness of the configuration.

Collectively, connectors should account for all connections required for the overall email topology design. Simple Mail Transfer Protocol (SMTP) connectors, when listed, must name purpose and direction clearly, and their counterparts on servers to which they connect should be recognizable as their partners.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select Name, Identity

Review the naming for connectors. If the connectors are not clearly named for purpose and direction, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SendConnector -Name <'NewName'> -Identity <'SendConnector'>

V-33586 No Change

Findings ID:	Exch-2-754	Rule ID:	SV-44006r1_rule	Severity:	low	CCI:

Discussion

This setting controls the rate at which delivery attempts from the home domain are retried, user notifications are issued, and notes the expiration time when the message will be discarded.

If delivery retry attempts are too frequent, servers will generate network congestion. If too far apart, then messages may remain queued longer than necessary, potentially raising disk resource requirements.

The default values of these fields should be adequate for most environments. Administrators may wish to modify the values as a result, but changes should be documented in the System Security Plan.

NOTE: Transport configuration settings apply to the organization/global level of the Exchange SMTP path. By checking and setting them at the Hub server the setting will apply to both Hub and Edge roles.ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the value for 'Transient Failure Retry Count'.

Open the Exchange Management Shell and enter the following command:

Get-TransportServer -Identity <'ServerUnderReview'> | Select Name, Identity, TransientFailureRetryCount

If the value of 'TransientFailureRetryCount' is set to 10 or less, this is not a finding.

If the value of 'TransientFailureRetryCount' is set to more than 10, and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-TransportServer -Identity <'ServerUnderReview'> -TransientFailureRetryCount 10 or other value as identified by the EDSP.

V-33587 Updated

Findings ID:	Exch-2-757	Rule ID:	SV-44007r3_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound message size. Failure to control the configuration strategy can result in loss of data or system availability.

This setting enables the administrator to control the maximum message size on a send connector. Using connectors to control size limits may necessitate the need to apply message size limitations in multiple places, with the potential of introducing conflicts and impediments in the mail flow. Changing this setting at the connector overrides the global one. Therefore, if operational needs require it, the connector value may be set lower than that of the global value with the rationale and documented in the EDSP.~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message send size and if signoff with risk acceptance is documented for the receive connector to have a different value.

Open the Exchange Management Shell and enter the following command:
Get-SendConnector | Select Identity, MaxMessageSize

or

Get-TransportConfig | Select Identity, MaxSendSize

If 'MaxMessageSize' is set to a numeric value different from the global value, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of ‘MaxMessageSize' is not the same as the global value, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SendConnector -Identity <'SendConnector'> -MaxMessageSize <MaxSendSize>

If an alternate value is desired from the global value MaxSendSize, obtain signoff with risk acceptance and document in the EDSP.

V-33589 No Change

Findings ID:	Exch-2-760	Rule ID:	SV-44009r1_rule	Severity:	low	CCI:

Discussion

This setting controls the maximum number of simultaneous outbound connections allowed for a given SMTP Connector, and can be used to throttle the SMTP service if resource constraints warrant it. If the limit is too low, connections may be dropped. If too high, some domains may use a disproportionate resource share, denying access to other domains. Appropriate tuning reduces risk of data delay or loss.
ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the value for 'SMTP Server Maximum Outbound Connections'.

Open the Exchange Management Shell and enter the following command:

Get-TransportServer -Identity <'ServerUnderReview'> | Select Name, Identity, MaxOutboundConnections

If the value of 'MaxOutboundConnections' is set to 1000 this is not a finding.

If the value of 'MaxOutboundConnections' is set to a value other than 1000 and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-TransportServer -Identity <'ServerUnderReview'> -MaxOutboundConnections 1000.

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33590 No Change

Findings ID:	Exch-2-763	Rule ID:	SV-44010r1_rule	Severity:	medium	CCI:

Discussion

The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. There are several controls that work together to provide security between internal servers. This setting controls the authentication method used for communications between servers. With this feature enabled, only servers capable of supporting domain authentication will be able to send and receive mail within the domain.

The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from server to server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender.

Individually, channel security and encryption can be compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between servers.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select Name, Identity, DomainSecureEnabled

If the value of 'DomainSecureEnabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SendConnector <'InternalSendConnector'> -DomainSecureEnabled $true

V-33592 Updated

Findings ID:	Exch-2-766	Rule ID:	SV-44012r13_rule	Severity:	medium	CCI:

Discussion

The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. There are several controls that work together to provide security between internal servers. This setting controls the encryption method used for communications between servers. With this feature enabled, only servers capable of supporting Transport Layer Security (TLS) will be able to send and receive mail within the domain.

The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from server to server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender.

Individually, channel security and encryption can be compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between servers.~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select Name, Identity, TlsDomain

If the value of 'TlsDomain' is not set to ~~'True'~~the value of the internal <'SMTP Domain'>, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SendConnector -Identity <'SendConnector'> -TlsDomain ~~$true~~<'SMTP Domain'>

<'SMTP Domain'>

Note: 'SMTP Domain' is the internal SMTP domain within the organization.

V-33594 Updated

Findings ID:	Exch-2-771	Rule ID:	SV-44014r12_rule	Severity:	medium	CCI:

Discussion

In the case of identifying a 'Smart Host' for the email environment, ~~the~~a logical send connector ~~level~~ is the preferred ~~location for this configuration because flow control in this routing group will be retained even if future changes occur at the Receive Connector level.~~ method.

A 'Smart Host' ~~(Edge Transport Server) Role~~ acts as an Internet Facing Concentrator for other email servers. Appropriate hardening can be applied to the ~~Edge Transport Server (Email Secure Gateway) role~~Smart Host rather than at multiple locations throughout the enterprise. ~~The 'Smart Host' performs all Domain Name Service (DNS) lookups to determine mail routing and offers some proxy-type benefits.~~

Failure to identify a 'Smart Host' could default to each email server performing its own lookups (potentially through protective firewalls). Exchange servers should not be Internet facing, and should therefore not perform any 'Smart Host' functions. TWhen the Exchange servers are Internet facing they must, however, be configured to identify the Internet facing server that is performing the 'Smart Host' function.~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select Name, Identity, SmartHosts

Identify ~~non-~~the Internet facing connectors.

If the value of 'SmartHosts' does not return the Smart Host IP Address, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SendConnector <'SendConnector'> -SmartHosts <'IP Address of Smart Host'> -DNSRoutingEnabled $false

V-33596 No Change

Findings ID:	Exch-2-801	Rule ID:	SV-44016r1_rule	Severity:	medium	CCI:

Discussion

A connectivity log is a record of the SMTP connection activity of the outbound message delivery queues to the destination Mailbox server, smart host, or domain. Connectivity logging is available on Hub Transport servers and Edge Transport servers. By default, connectivity logging is disabled. If events are not recorded it may be difficult or impossible to determine the root cause of system problems or the unauthorized activities of malicious users.

NOTE: Transport configuration settings apply to the organization/global level of the Exchange SMTP path. By checking and setting them at the Hub server the setting will apply to both Hub and Edge roles.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-TransportServer -Identity <'ServerUnderReview'> | Select Name, Identity, ConnectivityLogEnabled

If the value of 'ConnectivityLogEnabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-TransportServer -Identity <'ServerUnderReview'> -ConnectivityLogEnabled $true

V-33598 No Change

Findings ID:	Exch-2-805	Rule ID:	SV-44018r1_rule	Severity:	medium	CCI:

Discussion

Attackers can use automated messages to determine whether a user account is active, in the office, traveling, and so on. An attacker might use this information to conduct future attacks. Ensure that delivery reports to remote domains are disabled. Before enabling this setting first configure a remote domain using the EMC or the New-RemoteDomain cmdlet.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-RemoteDomain | select identity, DeliveryReportEnabled

If the value of 'DeliveryReportEnabled' is not set to 'False', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-RemoteDomain -Identity <'RemoteDomainName'> -DeliveryReportEnabled $false

V-33599 No Change

Findings ID:	Exch-2-808	Rule ID:	SV-44019r1_rule	Severity:	medium	CCI:

Discussion

Attackers can use automated messages to determine whether a user account is active, in the office, traveling, and so on. An attacker might use this information to conduct future attacks. Ensure that non-delivery reports to remote domains are disabled. Before enabling this setting first configure a remote domain using the EMC or the New-RemoteDomain cmdlet.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-RemoteDomain | select identity, NDREnabled

If the value of 'NDREnabled' is not set to 'False', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-RemoteDomain -Identity <'RemoteDomainName'> -NDREnabled $false

V-33601 No Change

Findings ID:	Exch-2-811	Rule ID:	SV-44021r1_rule	Severity:	medium	CCI:

Discussion

SPAM originators, in an effort to refine mailing lists, sometimes use a technique where they monitor transmissions for automated bounce back messages, such as 'Out of Office' messages. Automated messages include such items as Out of Office responses, non-delivery messages, or automated message forwarding.

Automated bounce back messages can be used by a third party to determine if users exist on the server. This can result in the disclosure of active user accounts to third parties, paving the way for possible future attacks. ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-RemoteDomain -Identity 'default' | Select Name, Identity, AllowedOOFType

If the value of 'AllowedOOFType' is set to 'External' or 'ExternalLegacy', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-RemoteDomain -AllowedOOFType 'InternalLegacy' -Identity 'default'

V-33603 No Change

Findings ID:	Exch-2-814	Rule ID:	SV-44023r1_rule	Severity:	medium	CCI:

Discussion

Attackers can use automated messages to determine whether a user account is active, in the office, traveling, and so on. An attacker might use this information to conduct future attacks. Remote users will not receive automated 'Out Of Office' delivery reports. This setting can be used to determine if all the servers in the Organization can send 'Out of Office' messages.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-RemoteDomain | select identity, AutoReplyEnabled

If the value of 'AutoReplyEnabled' is not set to 'False', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-RemoteDomain -Identity <'RemoteDomainName'> -AutoReplyEnabled $false

V-33606 Updated

Findings ID:	Exch-2-817	Rule ID:	SV-44026r12_rule	Severity:	medium	CCI:

Discussion

Log files help establish a history of activities, and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Diagnostic logging, however, characteristically produces large volumes of data and requires care in managing the logs to prevent risk of disk capacity denial of service conditions.

Exchange diagnostic logging is broken up into 29 main '“services'”, each of which has anywhere from 2 to 26 '“categories'” of events to be monitored. Moreover, each category may be set to one of four levels of logging: Lowest, Low, Medium, and High, depending on how much detail one desires. The higher the level of detail, the more disk space required to store the audit material.

Diagnostic logging is intended to help administrators debug problems with their systems, not as a general purpose auditing tool. Because the diagnostic logs collect a great deal of information, the log files may grow huge very quickly. Diagnostic log levels may be raised for limited periods of time when attempting to debug relevant pieces of Exchange functionality. Once debugging has finished, diagnostic log levels should be reduced again.~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-EventLogLevel

If any Diagnostic '“EventLevel'” is not set to “Lowo� LowestL, this is a finding.f

Fix

Open the Exchange Management Shell and enter the following command:

Set-EventLogLevel -Identity <ServiceName\Name> -Level Lowest

or

Set-EventLogLevel -Identity <ServiceName\Name> -Level Low

V-33608 Updated

Findings ID:	Exch-2-820	Rule ID:	SV-44028r2_rule	Severity:	medium	CCI:

Discussion

Log files help establish a history of activities, and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. This setting enables an automated log entry to be sent to Microsoft giving general details about the nature and location of the error. Microsoft, in turn, uses this information to improve the robustness of their product.

While this type of debugging information would not ordinarily contain sensitive information, it may alert eavesdroppers to the existence of problems in your Exchange organization. At the very least, it could alert them to (possibly) advantageous timing to mount an attack. At worst, it may provide them with information as to which aspects of Exchange are causing problems and might be vulnerable (or at least sensitive) to attack.

All system errors in Exchange will result in outbound traffic that may be identified by an eavesdropper. For this reason, the 'Report Fatal Errors to Microsoft' feature must be disabled.~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-ExchangeServer –status | Select Name, Identity, ErrorReportingEnabled

If the value of 'ErrorReportingEnabled' is not set to 'False', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ExchangeServer -Identity <'ServerName'> -ErrorReportingEnabled $false

V-33611 No Change

Findings ID:	Exch-2-826	Rule ID:	SV-44031r1_rule	Severity:	medium	CCI:

Discussion

Log files help establish a history of activities, and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Audit log content must always be considered sensitive, and in need of protection. Audit data available for modification by a malicious user can be altered to conceal malicious activity. Audit data might also provide a means for the malicious user to plan unauthorized activities that exploit weaknesses.

The contents of audit logs are protected against unauthorized access, modification, or deletion. Only authorized auditors and the audit functions should be granted Read and Write access to audit log data.ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the authorized groups or users that should have access to the audit data.

If any group or user has access to the audit data that is not documented in the EDSP, this is a finding.

Fix

Restrict any unauthorized groups or users from accessing the audit logs.

V-33613 No Change

Findings ID:	Exch-2-828	Rule ID:	SV-44033r1_rule	Severity:	medium	CCI:

Discussion

Default product installations may provide more generous access permissions than are necessary to run the application. By examining and tailoring access permissions to more closely provide the least amount of privilege possible, attack vectors that align with user permissions are less likely to access more highly secured areas.ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the authorized groups and users that have access to the Exchange application directories.

Verify the access permissions on the directory match the access permissions listed in the EDSP. If any group or user has different access permissions, this is a finding.

Note: The default installation directory is \Program Files\Microsoft\Exchange Server\V14.

Fix

Locate the Exchange application directory and Remove or modify the group or user access permissions.

Note: The default installation directory is \Program Files\Microsoft\Exchange Server\V14.

V-33616 No Change

Findings ID:	Exch-2-831	Rule ID:	SV-44036r1_rule	Severity:	medium	CCI:

Discussion

Log files help establish a history of activities, and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. This setting enables an automated entry to be sent to Microsoft giving general details about how the product is used. Microsoft, in turn, uses this information to improve the robustness of their product.

While this type of information does not ordinarily contain sensitive information, it may alert eavesdroppers to the existence of the environment and its configurations. It could alert them to (possibly) advantageous timing or weaknesses toward which to mount an attack.
ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-OrganizationConfig
If the value for CustomerFeedbackEnabled is not set to 'False', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-OrganizationConfig -CustomerFeedbackEnabled $false

V-33618 No Change

Findings ID:	Exch-2-839	Rule ID:	SV-44038r1_rule	Severity:	medium	CCI:

Discussion

Log files help establish a history of activities, and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. Audit log content must always be considered sensitive, and in need of protection.

Successful exploit of an application server vulnerability may well be logged by monitoring or audit processes when it occurs. By writing log and audit data to a separate partition where separate security contexts protect them, it may offer the ability to protect this information from being modified or removed by the exploit mechanism.ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the audit logs assigned partition.

By default the logs are located on the application partition in '\Program Files\Microsoft\Exchange Server\V14\Logging\'.

If the log files are not on a separate partition from the application, this is a finding.

Fix

Configure the audit log location to be on a partition drive separate from the application.

Document the location in the EDSP.

V-33619 Updated

Findings ID:	Exch-2-842	Rule ID:	SV-44039r13_rule	Severity:	medium	CCI:

Discussion

Monitors are automated '“process watchers'” that respond to performance changes, and can be useful in detecting outages and alerting administrators where attention is needed. Exchange has built-in monitors that enable the administrator to generate alerts if thresholds are reached, better enabling them to react in a timely fashion.

This field offers choices of alerts when a 'warning' or 'critical' threshold is reached on the SMTP queue. A good rule of thumb (default) is to issue warnings when SMTP queue growth exceeds 10 minutes and critical messages when it exceeds 20 minutes, which should only exist occasionally. Frequent alerts against this counter may indicate a network or other issue (such as inbound SPAMMER traffic) that directly impacts email delivery. e intent of this check is for system administrators to have awareness of performance changes on their network.

Notification choices include email an alert to an email -enabled account, for example, an email Administrator, or invoke a script to take other action, for example, to add an Event to the Microsoft Application Event Log, where external monitors might detect it.~~ECSC-1~~

Data elements configured to be monitored should be specific to the organization’s tetwork.

Checks

Note: If a third -party application is performing monitoring functions, the reviewer should verify the application is monitoring correctly and mark the vulnerability NA.

~~To review data collection sets used for monitoring~~Open the Exchange Management Shell and enter the following command:

perfmon

~~Click on th~~In the left pane, expand and navigate Data Collect~~ion~~or Sets ~~icon, Click the User Defined folder, right click the data collection set~~>> User Defined.
If no sets are defined or queues are not being monitored, this is a finding.

Fix

Open the Exchange Management Console.
Expand the tree in the left column.
Click the Exchange Toolbox icon.
C

In the left pane, navigate to and select Microsoft Exchange On-Premises <server.domain> --> Toolbox

In the Right pane double click on Performance Monitor

In the left pane, navigate to and select Performance Logs and Alerts --> Data Collector Sets --> User Defined

Right click on User Defined and configure the system to use User Defined data collection for monitoring the queues.

V-33620 No Change

Findings ID:	Exch-3-003	Rule ID:	SV-44040r1_rule	Severity:	medium	CCI:

Discussion

The INFOCON system provides a framework within which the Commander USSTRATCOM regional commanders, service chiefs, base/post/camp/station/vessel commanders, or agency directors can increase the measurable readiness of their networks to match operational priorities. The readiness strategy provides the ability to continuously maintain and sustain one’s own information systems and networks throughout their schedule of deployments, exercises, and operational readiness life cycle independent of network attacks or threats. The system provides a framework of prescribed actions and cycles necessary for reestablishing the confidence level and security of information systems for the commander and thereby supporting the entire Global Information Grid (GIG) (SD 527-1 Purpose).

The Exchange software files and directories are vulnerable to unauthorized changes if not adequately protected. An unauthorized change could affect the integrity or availability of email services overall. For this reason, all application software installations must monitor for change against a software baseline that is preserved when installed, and updated periodically as patches or upgrades are installed. Automated and manual schedules for software change monitoring must be compliant with SD527-1 frequencies.

Note: Policy Auditor 5.2 or later, File Integrity Monitor (FIM) module will meet the requirement for file integrity checking. The Asset module within HBSS does not meet this requirement.
ECSC-1

Checks

Access the EDSP baseline section and determine the process and frequency for identifying software changes (*.exe, *.bat, *.com, *.cmd, and *.dll) on servers against a baseline.

Examine artifacts identified as outputs of this process.

If baseline comparisons are not done on the INFOCON-required schedule, this is a finding.

Fix

Implement a process to compare software against a baseline (*.exe, *.bat, *.com, *.cmd, and *.dll) on a frequency required by the prevailing INFOCON level.

Document the process and output artifacts in the EDSP.

V-33621 No Change

Findings ID:	Exch-3-006	Rule ID:	SV-44041r1_rule	Severity:	medium	CCI:

Discussion

Exchange software, as with other application software installed on a host system, must be included in a system baseline record and periodically reviewed; otherwise unauthorized changes to the software may not be discovered. This effort is a vital step to securing the host and the applications, as it is the only method that may provide the ability to detect and recover from otherwise undetected changes, such as those that result from worm or bot intrusions.

The Exchange software and configuration baseline is created and maintained for comparison during scanning efforts. Operational procedures must include baseline updates as part of configuration management tasks that change the software and configuration.
ECSC-1

Checks

Access the EDSP and locate the baseline documentation.

Review the application software baseline procedures and implementation artifacts. Note the list of files and directories included in the baseline procedure for completeness.

If an email software copy exists to serve as a baseline and is available for comparison during scanning efforts, this is not a finding.

Fix

Implement email software baseline process. Document the details in the EDSP.

V-33622 No Change

Findings ID:	Exch-2-005	Rule ID:	SV-44042r1_rule	Severity:	medium	CCI:

Discussion

Exchange may be configured to accept email for multiple domain names. This setting identifies the domains for which the server will accept mail. This check verifies the email server is not accepting email for unauthorized domains.ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the 'Accepted Domain' values.

Open the Exchange Management Shell and enter the following command:

Get-AcceptedDomain

If the value for 'AcceptedDomains' is not set to the value in the EDSP, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-AcceptedDomain -Identity <'ValueInEDSP'> -MakeDefault $true

V-33623 Updated

Findings ID:	Exch-3-804	Rule ID:	SV-44043r12_rule	Severity:	medium	CCI:

Discussion

Unneeded, but running, services offer attackers an enhanced attack profile, and attackers are constantly watching to discover open ports with running services. By analyzing and disabling unneeded services, the associated open ports become unresponsive to outside queries, and servers become more secure as a result.

Exchange Server has role-based server deployment to enable protocol path control and logical separation of network traffic types.

For example, a server implemented in the Client Access role (i.e., Outlook Web App [OWA]) is configured and tuned as a web server using web protocols. A client access server exposes only web protocols (HTTP/HTTPS) enabling system administrators to optimize the protocol path and disable all services unnecessary for Exchange web services. Similarly, servers created to host mailboxes are dedicated to that task, and must operate only the services needed for mailbox hosting. (Exchange servers must also operate some Web services, but only to the degree that Exchange requires the IIS engine in order to function).

Because POP3, and IMAP4 clients are not included in the standard desktop offering, they must be disabled.~~ECSC-1~~

Checks

To view system services open a windows power shell and enter the following command:

Get-Service | Where-Object {$_.status -eq 'running'}

The command returns a list of installed services and the status of that service.

Required services will vary between organizations, and will vary depending on the role of the individual system. Organizations will develop their own list of services which will be documented and justified with the IASSO. The Site’s list will be provided for any security review. Services that are common to multiple systems can be addressed in one document. Exceptions for individual systems should be identified separately by system.

If the site has not documented the services required for their system(s), this is a finding.

If any undocumented or unnecessary services are running, then this is a finding.

Fix

Document the services required for the system to operate. Remove or disable any services that are not required.

V-33624 No Change

Findings ID:	Exch-2-011	Rule ID:	SV-44044r1_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. Message size limits should be set to 10 megabytes at most, but often are smaller, depending on the organization. The key point in message size is that it should be set globally, and it should not be set to ‘unlimited’. Selecting ‘unlimited’ on either field is likely to result in abuse and can contribute to excessive server disk space consumption.

Message size limits may also be applied on SMTP connectors, Public Folders, and on the user account under AD. Changes at these lower levels are discouraged, as the single global setting is usually sufficient. This practice prevents conflicts that could impact availability and it simplifies server administration.

ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message receive size.

Open the Exchange Management Shell and enter the following command:
Get-TransportConfig | Select Identity, MaxReceiveSize

If the value of 'MaxReceiveSize' is set to 10MB, this is not a finding.

If the value of 'MaxReceiveSize' is set to an alternate value, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of 'MaxReceiveSize' is set to “Unlimited”, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-TransportConfig -MaxReceiveSize 10MB

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33625 Updated

Findings ID:	Exch-3-807	Rule ID:	SV-44045r13_rule	Severity:	medium	CCI:

Discussion

In the same way that added security layers can provide a cumulative positive effect on security posture, multiple applications can provide a cumulative negative effect. A vulnerability and subsequent exploit to one application can lead to an exploit of other applications sharing the same security context. For example, an exploit to a web server process that leads to unauthorized administrative access to the host system can most likely lead to a compromise of all applications hosted by the same system.

Email services should be installed on a partition that does not host other applications. Email services should never be installed on a Domain Controller / Directory Services server. ~~ECSC-1~~

Checks

Access Windows Explorer and identify the OS partition. Navigate to configured partitions, and access the ‘Program Files’ directory.

NMake note of the installation partition for Microsoft Exchange.

If Microsoft Exchange resides on a partition other than that of the OS, and does not have other applications installed ~~(without associated approval from the IAO)~~, this is not a finding.
Note: In the case where additional applications are installed on the same partition as Microsoft Exchange, and each of those additional applications have been documented and had a risk assessment completed by the ISSO/ISSM, this is not a finding.

Fix

Install Exchange on a dedicated application partition separate than that of the OS.

V-33626 Updated

Findings ID:	Exch-2-014	Rule ID:	SV-44046r2_rule	Severity:	medium	CCI:

Discussion

Server certificates are required for many security features in Exchange; without them the server cannot engage in many forms of secure communication.
Failure to implement valid certificates makes it virtually impossible to secure Exchange's communications.~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-ExchangeCertificate | Select CertificateDomains, issuer

If the value of 'CertificateDomains' does not indicate it is issued by the DoD, this is a finding.

Fix

Remove the non-DoD certificate and import the correct DoD certificates.

V-33627 Updated

Findings ID:	Exch-2-015	Rule ID:	SV-44047r2_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. Message size limits should be set to 10 megabytes at most, but often are smaller, depending on the organization. The key point in message size is that it should be set globally, and it should not be set to ‘unlimited’. Selecting ‘unlimited’ on either field is likely to result in abuse and can contribute to excessive server disk space consumption.

Message size limits may also be applied on send and receive connectors, Public Folders, and on the user account under AD. Changes at these lower levels are discouraged, as the single global setting is usually sufficient. This practice prevents conflicts that could impact availability and it simplifies server administration.~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message send size.

Open the Exchange Management Shell and enter the following command:
Get-TransportConfig | Select Identity, MaxSendSize

If the value of 'MaxSendSize' is set to 10MB, this is not a finding.

If the value of 'MaxSendSize' is set to an alternate value, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of 'MaxSendSize' is set to “Unlimited”, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-TransportConfig -MaxSendSize 10MB

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33629 Updated

Findings ID:	Exch-3-814	Rule ID:	SV-44049r23_rule	Severity:	medium	CCI:

Discussion

Failure to install the most current Exchange service pack leaves a system vulnerable to exploitation. Current service packs correct known security and system vulnerabilities.
~~ECSC-1~~

Checks

Open the Exchange Management Shell and enter the following command:

Get-ExchangeServer | fl name, AdminDisplayVersion

If the value of 'AdminDisplayVersion' does not return Version 14.2 (Build 247.5) for ~~Exchange 2010 Service pack 2~~greater, this is a finding.

Fix

~~Install the current approved service pack, Exchange 2010 Service pack 2~~Update the system with the latest approved service pack or a supported release.

V-33630 No Change

Findings ID:	Exch-2-017	Rule ID:	SV-44050r1_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. The Global Recipient Count limit field is used to control the maximum number of recipients that can be specified in a single message sent from this server. Its primary purpose is to minimize the chance of an internal sender spamming other recipients, since SPAM messages often have a large number of recipients. SPAM prevention can originate from both outside and inside organizations. While inbound SPAM is evaluated as it arrives, controls such as this one help prevent SPAM that might originate inside the organization.

The Recipient Count Limit is global to the Exchange implementation. Lower-level refinements are possible; however, in this configuration strategy, setting the value once at the global level ensures a more available system by eliminating potential conflicts among multiple settings. A value of less than or equal to 5000 is probably larger than is needed for most organizations, but is small enough to minimize usefulness to spammers, and is easily handled by Exchange. An unexpanded distribution is handled as one recipient. Specifying “unlimited” may result in abuse.
ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message recipient count.

Open the Exchange Management Shell and enter the following command:

Get-TransportConfig | Select Identity, MaxRecipientEnvelopeLimit
If the value of 'MaxRecipientEnvelopeLimit' is set to 5000, this is not a finding.

If the value of 'MaxRecipientEnvelopeLimit' value is set to an alternate value, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of 'MaxRecipientEnvelopeLimit' is set to 'Unlimited', this is a finding.

Fix

Set-transportConfig -'MaxRecipientEnvelopeLimit' 5000

Restart the “Microsoft Exchange Information Store” service.

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33631 No Change

Findings ID:	Exch-2-333	Rule ID:	SV-44051r1_rule	Severity:	medium	CCI:

Discussion

Sender Identification (SID) is an email anti-spam sanitization process. Sender ID uses DNS MX record lookups to verify the SMTP sending server is authorized to send email for the originating domain.

Failure to implement Sender ID risks that SPAM could be admitted into the email domain that originates from rogue servers. Most SPAM content originates from domains where the IP address has been spoofed prior to sending, thereby avoiding detection. For example, messages with malformed or incorrect 'purported responsible sender' data in the message header could be (best case) created by using RFI non-compliant software, but is more likely to be SPAM.

ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-SenderIdConfig | Select Name, Identity, SpoofedDomainAction

If the value of 'SpoofedDomainAction' is not set to 'Reject', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderIdConfig -SpoofedDomainAction Reject

V-33632 No Change

Findings ID:	Exch-2-019	Rule ID:	SV-44052r1_rule	Severity:	medium	CCI:

Discussion

Scripts often provide a way for attackers to infiltrate a system, especially those downloaded from untrusted locations. By setting machine policy to prevent unauthorized script executions, unanticipated system impacts can be avoided. Failure to allow only signed remote scripts reduces the attack vector vulnerabilities from unsigned remote scripts. ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ExecutionPolicy

If the value of 'LocalMachine' does not return a value of 'RemoteSigned', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ExecutionPolicy RemoteSigned

V-33633 Updated

Findings ID:	Exch-2-330	Rule ID:	SV-44053r2_rule	Severity:	medium	CCI:

Discussion

Block List filtering is a sanitization process performed on email messages prior to their arrival at the destination mailbox. By performing this process at the email perimeter, threats can be eliminated outside the enclave, where there is less risk they can do harm.

Block List Services (sometimes called Reputation Data Services) are fee based data providers that collect the IP addresses of known SPAMmers and other malware purveyors. Block List Service Subscribers benefit from more effective SPAM elimination, which has been estimated as comprising up to 90% of inbound mail volume. Failure to specify a Block List provider risks that manual email administration effort would be needed to maintain and update larger block lists than a single email site administrator could conveniently or accurately maintain.

The 'Block List' Services vendor provides a value for this field, usually the DNS suffix for their domain.~~ECSC-1~~

Checks

Access the EDSP for the name and information for the Block List provider.

Open the Exchange Management Shell and enter the following command:
Get-IPBlockListProvider | Select Name Identity LookupDomain

If the values for Name, GUID and LookupDomain are configured, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-IPBlockListProvider -Name <Provider Name> [Additional optional parameters as required by the service provider]

Document the configuration in the EDSP.

V-33634 No Change

Findings ID:	Exch-2-200	Rule ID:	SV-44054r1_rule	Severity:	medium	CCI:

Discussion

Automated connection responses occur as a result of FTP or Telnet connections, when connecting to those services. They report a successful connection by greeting the connecting client, stating the name, release level, and (often) additional information regarding the responding product. While useful to the connecting client, connection responses can also be used by a third party to determine operating system (OS) or product release levels on the target server. The result can include disclosure of configuration information to third parties, paving the way for possible future attacks. For example, when querying the SMTP service on port 25, the default response looks similar to this one:

220 exchange.mydomain.org Microsoft ESMTP MAIL Service, Version: 6.0.3790.211 ready at Wed, 2 Feb 2005 23:40:00 -0500

Changing the response to hide local configuration details reduces the attack profile of the target.
ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select Name, Identity, Banner

If the value of 'Banner' is not set to '220 SMTP Server Ready', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -Banner '220 SMTP Server Ready'

V-33635 Updated

Findings ID:	Exch-2-201	Rule ID:	SV-44055r2_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous outbound connections from a domain, and works in conjunction with the Maximum Outbound Connections Count setting as a delivery tuning mechanism. If the limit is too low, connections may be dropped. If too high, some domains may use a disproportionate resource share, denying access to other domains. Appropriate tuning reduces risk of data delay or loss.

By default, a limit of 20 simultaneous outbound connections from a domain should be sufficient. The value may be adjusted if justified by local site conditions.~~ECSC-1~~

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the value for 'Maximum Domain Connections' and the server under review.

Open the Exchange Management Shell and enter the following command:

Get-TransportServer -Identity
<'ServerUnderReview'> | Select Name, Identity, MaxPerDomainOutboundConnections

If the value of 'MaxPerDomainOutboundConnections' is set to 20 this is not a finding.

If the value of 'MaxPerDomainOutboundConnections' is set to a value other than 20 and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-TransportServer -Identity <'ServerUnderReview'> -MaxPerDomainOutboundConnections 20

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33636 No Change

Findings ID:	Exch-2-327	Rule ID:	SV-44056r1_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages may be eliminated from the transport message stream, preventing their entry into the Exchange environment. This significantly reduces the attack vector for inbound email-borne SPAM and malware.
SPAM evaluation (heuristic) filters scan inbound email messages for evidence of SPAM and other attacks that primarily use 'Social Engineering' techniques. Upon evaluation completion, a rating is assigned to each message estimating the likelihood of its being SPAM. Upon arrival at the destination mailbox, the junk mail filter threshold (also configurable) determines whether the message will be withheld from delivery, delivered to the junk mail folder, or delivered to the user’s inbox.
ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ContentFilterConfig | Select Name, Identity, Enabled

If the value of 'Enabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ContentFilterConfig -Enabled $true

V-33637 Updated

Findings ID:	Exch-2-302	Rule ID:	SV-44057r12_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90~~% of SPAM~~ percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. Attachments are being used more frequently for different forms of attacks. By filtering undesirable attachments a large percent of malicious code can be prevented from entering the system. Attachments must be controlled at the entry point into the email environment to prevent successful attachment-based attacks. The following is a basic list of known attachments that should be filtered from Internet mail attachments.

*.ade *.crt *.jse *.msi *.scr *.wsh *.dir
*.adp *.csh *.ksh *.msp *.sct *.htm *.dcr
*.app *.exe *.lnk *.mst *.shb *.html *.plg
*.asx *.fxp *.mda *.ops *.shs *.htc *.spl
*.bas *.hlp *.mdb *.pcd *.url *.mht *.swf
*.bat *.hta *.mde *.pif *.vb *.mhtml *.zip
*.chm *.inf *.mdt *.prf *.vbe *.shtm
*.cmd *.ins *.mdw *.prg *.vbs *.shtml
*.com *.isp *.mdz *.reg *.wsc *.stm
*.cpl *.js *.msc *.scf *.wsf *.xml ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the list of undesirable attachment types that should be stripped.

Open the Exchange Management Shell and enter the following command:

Get-AttachmentFilterEntry

If the values returned are different from the EDSP documented attachment types, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Add-AttachmentFilterEntry -Name <'*.FileExtension'> -Type FileName

V-33638 No Change

Findings ID:	Exch-2-324	Rule ID:	SV-44058r1_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. Sender reputation is anti-SPAM functionality that blocks messages according to many characteristics of the sender. Sender reputation relies on persisted data about the sender to determine what action, if any, to take on an inbound message. This setting enables the threshold at which an email will be considered SPAM.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-SenderReputationConfig | Select SrlBlockThreshold

If the value of 'SrlBlockThreshold' is not set to '6', this is a finding.

If the value of 'SrlBlockThreshold' is set to a value other than 6 and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderReputationConfig -SrlBlockThreshold 6.

If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.

V-33639 No Change

Findings ID:	Exch-2-321	Rule ID:	SV-44059r1_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the Mail server environment. Sender reputation is anti-SPAM functionality that blocks messages according to many characteristics of the sender. Sender reputation relies on persisted data about the sender to determine what action, if any, to take on an inbound message. This setting enables the sender reputation function.ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-SenderReputationConfig | Select Enabled

If the value of 'Enabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderReputationConfig -Enabled $true

V-33640 No Change

Findings ID:	Exch-2-305	Rule ID:	SV-44060r1_rule	Severity:	medium	CCI:

Discussion

SPAM originators, in an effort to refine mailing lists, sometimes use a technique where they first create fictitious names, and then monitor rejected emails for non-existent recipients.
Those not rejected, of course, are deemed to exist, and are therefore used in future SPAM mailings.

To prevent this disclosure of existing email accounts to Spammers, this feature should not be employed. Instead, it is recommended that all messages be received, then evaluated and disposed of without enabling the sender to determine recipients that are existing vs. non-existing.
ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-RecipientFilterConfig | Select RecipientValidationEnabled

If the value of 'RecipientValidationEnabled' is not set to 'False', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-RecipientFilterConfig -RecipientValidationEnabled $False

V-33641 No Change

Findings ID:	Exch-2-317	Rule ID:	SV-44061r1_rule	Severity:	medium	CCI:

Discussion

SPAM origination sites and other sources of suspected Email-borne malware have the ability to corrupt, compromise, or otherwise limit availability of Email servers. Limiting exposure to unfiltered inbound messages can reduce the risk of SPAM and malware impacts.

The Global Deny list block messages originating from specific sources. Most Black List filtering is done using a commercial 'Block List' service, because eliminating threats from known SPAMMERS prevents the messages being evaluated inside the enclave where there is more risk they can do harm.

Additional sources should also be blocked to supplement the contents of the commercial 'Block List Service'. For example, during a 0-Day threat action, entries can be added, and then removed when the threat is mitigated. An additional best practice is to enter the enterprise’s home domains in the Deny List, because inbound Email with a ‘from’ address of the home domain is very likely to be SPOOFED SPAM. ECSC-1

Checks

Access the EDSP for the list of accepted domains for which this server accepts inbound email.

Open the Exchange Management Shell and enter the following command:

Get-SenderFilterConfig

If the value for 'BlockedDomains' or 'BlockedDomainsAndSubdomains' does not reflect the list of accepted domains, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderFilterConfig -BlockedDomains <domain list>
Or
Set-SenderFilterConfig -BlockedDomainsAndSubdomains <domain list>

Enter the list of accepted domains for this email system.
Document the configuration in the EDSP.

V-33642 No Change

Findings ID:	Exch-2-308	Rule ID:	SV-44062r1_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. This significantly reduces the attack vector for inbound Email-borne SPAM and malware.

As messages are filtered, it is prudent to temporarily host them in an archive for evaluation by administrators or users. The archive can be used to recover messages that might have been inappropriately filtered, preventing data loss, and to provide a base of analysis that can provide future filter refinements.
ECSC-1

Checks

Open the Exchange Management Shell and enter the following command:

Get-ContentFilterConfig | Select QuarantineMailbox

If no SMTP address is assigned to 'QuarantineMailbox', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ContentFilterConfig -QuarantineMailbox <'SmtpAddressOfMailbox'>

V-33643 Updated

Findings ID:	Exch-2-314	Rule ID:	SV-44063r12_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. Anonymous email (messages with blank sender fields) cannot be replied to. Messages formatted in this way may be attempting to hide their true origin to avoid responses, or to SPAM any receiver with impunity while hiding their source of origination.

Rather than spend resource and risk infection while evaluating them, it is recommended that these messages be filtered immediately upon receipt and not forwarded to end users.~~ECSC-1~~

Checks

This requirement is N/A for SIPR enclaves.

This requirement is N/A if the organization subscribes to EEMSG or other similar DoD enterprise protections for email services.

Open the Exchange Management Shell and enter the following command:

Get-SenderFilterConfig | Select BlankSenderBlockingEnabled

If the value of 'BlankSenderBlockingEnabled' is not set to 'True', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderFilterConfig -BlankSenderBlockingEnabled $true

V-33644 Updated

Findings ID:	Exch-2-311	Rule ID:	SV-44064r12_rule	Severity:	medium	CCI:

Discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. Anonymous Email (messages with blank sender fields) cannot be replied to. Messages formatted in this way may be attempting to hide their true origin to avoid responses, or to SPAM any receiver with impunity while hiding their source of origination.

Rather than spend resource and risk infection while evaluating them, it is recommended that these messages be filtered immediately upon receipt and not forwarded to end users.
~~ECSC-1~~

Checks

This requirement is N/A for SIPR enclaves.

This requirement is N/A if the organization subscribes to EEMSG or other similar DoD enterprise protections for email services.

Open the Exchange Management Shell and enter the following command:

Get-SenderFilterConfig | Select Action

If the value of 'Action ' is not set to 'Reject', this is a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-SenderFilterConfig -Action Reject

V-33646 No Change

Findings ID:	Exch-2-769	Rule ID:	SV-44066r1_rule	Severity:	low	CCI:

Discussion

Email system availability depends in part on best practices strategies for setting tuning configurations. This configuration controls the number of idle minutes before the connection is dropped. It works in conjunction with the Maximum Outbound Connections Count setting.

Connections, once established, may incur delays in message transfer. The default of 10 minutes is a reasonable window in which to resume activities without maintaining idle connections for excessive intervals. If the timeout period is too long, idle connections may be maintained for unnecessarily long time periods, preventing new connections from being established. Sluggish connectivity increases the risk of lost data. A value of 10 or less is optimal.
ECSC-1

Checks

Obtain the Email Domain Security Plan (EDSP) and locate the 'Connection Timeout' value.

Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select Name, Identity, ConnectionInactivityTimeOut

If the value of 'ConnectionInactivityTimeOut' is set to 00:10:00, this is not a finding.

If 'ConnectionInactivityTimeOut' is set to other than 00:10:00, and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix

Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'ReceiveConnector'> -ConnectionInactivityTimeOut
00:10:00 or other value as identified by the EDSP.

V-60981 Added

Findings ID:	Exch-2-768	Rule ID:	SV-75445r1_rule	Severity:	medium	CCI:

Discussion

The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. There are several controls that work together to provide security between internal servers. This setting controls the encryption method used for communications between servers. With this feature enabled, only servers capable of supporting Transport Layer Security (TLS) will be able to send and receive mail within the domain. The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from server to server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender. Individually, channel security and encryption can be compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between servers.

Checks

Open the Exchange Management Shell and enter the following command: Get-SendConnector | Select Name, Identity, TlsAuthLevel If the value of 'TlsAuthLevel' is not set to 'DomainValidation, this is a finding.

Fix

Open the Exchange Management Shell and enter the following command: Set-SendConnector -Identity <'SendConnector'> -TlsAuthLevel DomainValidation

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