Microsoft Exchange 2016 Mailbox Server Security Technical Implementation Guide

This Security Technical Implementation Guide is published as a tool to improve the security of Department of Defense (DoD) information systems. The requirements are derived from the National Institute of Standards and Technology (NIST) 800-53 and related documents. Comments or proposed revisions to this document should be sent via email to the following address: [email protected]

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Version / Release: V1R4

Published: 2019-10-01

Updated At: 2019-11-11 10:45:50

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    Vuln Rule Version CCI Severity Title Description Status Finding Details Comments
    SV-95333r1_rule EX16-MB-000010 CCI-001403 MEDIUM Exchange must have Administrator audit logging enabled. Unauthorized or malicious data changes can compromise the integrity and usefulness of the data. Automated attacks or malicious users with elevated privileges have the ability to effect change using the same mechanisms as email administrators. Auditing a
    SV-95335r1_rule EX16-MB-000020 CCI-000213 MEDIUM Exchange servers must use approved DoD certificates. 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 communicatio
    SV-95337r1_rule EX16-MB-000030 CCI-001368 MEDIUM Exchange auto-forwarding email to remote domains must be disabled or restricted. 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. Verify Automatic Forwards to remote domains are disabled, except for
    SV-95339r1_rule EX16-MB-000040 CCI-000169 MEDIUM Exchange Connectivity logging must be enabled. 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 defa
    SV-95341r1_rule EX16-MB-000050 CCI-000169 MEDIUM The Exchange Email Diagnostic log level must be set to the lowest level. 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
    SV-95343r1_rule EX16-MB-000060 CCI-000169 LOW Exchange Audit record parameters must be set. Log files help establish a history of activities and can be useful in detecting attack attempts. This item declares the fields that must be available in the audit log file in order to adequately research events that are logged. Audit records should incl
    SV-95345r1_rule EX16-MB-000070 CCI-000133 LOW Exchange Circular Logging must be disabled. Logging provides a history of events performed and can also provide evidence of tampering or attack. Failure to create and preserve logs adds to the risk that suspicious events may go unnoticed and raises the potential that insufficient history will be av
    SV-95347r4_rule EX16-MB-000080 CCI-000133 MEDIUM Exchange Email Subject Line logging must be disabled. Log files help establish a history of activities and can be useful in detecting attack attempts or determining tuning adjustments to improve availability. When "message tracking" is enabled, only the sender, recipients, time, and other delivery informatio
    SV-95349r1_rule EX16-MB-000090 CCI-000133 MEDIUM Exchange Message Tracking Logging must be enabled. A message tracking log provides a detailed log of all message activity as messages are transferred to and from a computer running Exchange. If events are not recorded, it may be difficult or impossible to determine the root cause of system problems or th
    SV-95351r1_rule EX16-MB-000100 CCI-000154 MEDIUM Exchange Queue monitoring must be configured with threshold and action. 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
    SV-95353r1_rule EX16-MB-000110 CCI-000381 MEDIUM Exchange Send Fatal Errors to Microsoft must be disabled. It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to
    SV-95355r1_rule EX16-MB-000120 CCI-000162 MEDIUM Exchange must protect audit data against unauthorized read access. 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 availabl
    SV-95357r1_rule EX16-MB-000130 CCI-000381 MEDIUM Exchange must not send Customer Experience reports to Microsoft. It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to
    SV-95359r1_rule EX16-MB-000140 CCI-000163 MEDIUM Exchange must protect audit data against unauthorized access. 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 availabl
    SV-95361r1_rule EX16-MB-000150 CCI-000164 MEDIUM Exchange must protect audit data against unauthorized deletion. 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 availabl
    SV-95363r1_rule EX16-MB-000160 CCI-001348 MEDIUM Exchange Audit data must be on separate partitions. 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
    SV-95365r1_rule EX16-MB-000170 CCI-001749 MEDIUM Exchange Local machine policy must require signed scripts. Scripts often provide a way for attackers to infiltrate a system, especially scripts downloaded from untrusted locations. By setting machine policy to prevent unauthorized script executions, unanticipated system impacts can be avoided. Failure to allow on
    SV-95367r1_rule EX16-MB-000180 CCI-000381 MEDIUM The Exchange Internet Message Access Protocol 4 (IMAP4) service must be disabled. IMAP4 is not approved for use within the DoD. It uses a clear-text-based user name and password and does not support the DoD standard for PKI for email access. User name and password could easily be captured from the network, allowing a malicious user to
    SV-95369r1_rule EX16-MB-000190 CCI-000381 MEDIUM The Exchange Post Office Protocol 3 (POP3) service must be disabled. POP3 is not approved for use within the DoD. It uses a clear-text-based user name and password and does not support the DoD standard for PKI for email access. User name and password could easily be captured from the network, allowing a malicious user to a
    SV-95371r1_rule EX16-MB-000200 CCI-001082 MEDIUM Exchange Mailbox databases must reside on a dedicated partition. 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 ot
    SV-95373r1_rule EX16-MB-000210 CCI-001178 MEDIUM Exchange Internet-facing Send connectors must specify a Smart Host. When identifying a "Smart Host" for the email environment, a logical Send connector is the preferred method. A Smart Host acts as an Internet-facing concentrator for other email servers. Appropriate hardening can be applied to the Smart Host, rather than
    SV-95375r1_rule EX16-MB-000220 CCI-001184 MEDIUM Exchange internal Receive connectors must require encryption. 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.
    SV-95377r1_rule EX16-MB-000270 CCI-001199 MEDIUM Exchange Mailboxes must be retained until backups are complete. Backup and recovery procedures are an important part of overall system availability and integrity. Complete backups reduce the chance of accidental deletion of important information and make it possible to have complete recoveries. It is not uncommon for
    SV-95379r1_rule EX16-MB-000290 CCI-001199 MEDIUM Exchange email forwarding must be restricted. Auto-forwarded email accounts do not meet the requirement for digital signature and encryption of Controlled Unclassified Information (CUI) and Personally Identifiable Information (PII) in accordance with DoDI 8520.2 (reference ee) and DoD Director for Ad
    SV-95381r1_rule EX16-MB-000300 CCI-001199 MEDIUM Exchange email-forwarding SMTP domains must be restricted. Auto-forwarded email accounts do not meet the requirement for digital signature and encryption of Controlled Unclassified Information (CUI) and Personally Identifiable Information (PII) in accordance with DoDI 8520.2 (reference ee) and DoD Director for Ad
    SV-95383r1_rule EX16-MB-000310 CCI-001094 LOW Exchange Mail quota settings must not restrict receiving mail. Mail quota settings control the maximum sizes of a user’s mailbox and the system’s response if these limits are exceeded. Mailbox data that is not monitored against a quota increases the risk of mail loss due to filled disk space, which can also rende
    SV-95385r1_rule EX16-MB-000320 CCI-001094 LOW Exchange Mail Quota settings must not restrict receiving mail. Mail quota settings control the maximum sizes of a user’s mailbox and the system’s response if these limits are exceeded. Mailbox data that is not monitored against a quota increases the risk of mail loss due to filled disk space, which can also rende
    SV-95387r1_rule EX16-MB-000340 CCI-001094 LOW Exchange Mailbox Stores must mount at startup. Administrator responsibilities include the ability to react to unplanned maintenance tasks or emergency situations that may require Mailbox data manipulation. Occasionally, there may be a need to start the server with "unmounted" data stores if manual mai
    SV-95389r1_rule EX16-MB-000350 CCI-001095 LOW Exchange Message size restrictions must be controlled on Receive connectors. Email system availability depends in part on best practice 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 strateg
    SV-95391r1_rule EX16-MB-000360 CCI-001095 LOW Exchange Receive connectors must control the number of recipients per message. Email system availability depends in part on best practice 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 thro
    SV-95393r1_rule EX16-MB-000380 CCI-001095 LOW The Exchange Receive Connector Maximum Hop Count must be 60. Email system availability depends in part on best practice 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 I
    SV-95395r1_rule EX16-MB-000410 CCI-001095 LOW Exchange Message size restrictions must be controlled on Send connectors. Email system availability depends in part on best practice 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 strateg
    SV-95397r1_rule EX16-MB-000420 CCI-001095 LOW The Exchange Send connector connections count must be limited. The Exchange Send connector 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 m
    SV-95399r1_rule EX16-MB-000430 CCI-001095 LOW The Exchange global inbound message size must be controlled. Email system availability depends in part on best practice strategies for setting tuning configurations. Message size limits should be set to 10 megabytes (MB) at most but often are smaller, depending on the organization. The key point in message size is
    SV-95401r1_rule EX16-MB-000440 CCI-001095 LOW The Exchange global outbound message size must be controlled. Email system availability depends in part on best practice strategies for setting tuning configurations. Message size limits should be set to 10 megabytes (MB) at most but often are smaller, depending on the organization. The key point in message size is
    SV-95403r1_rule EX16-MB-000450 CCI-001095 LOW The Exchange Outbound Connection Limit per Domain Count must be controlled. Email system availability depends in part on best practice strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous outbound connections from a domain as a delivery tuning mechanism. If the limit is too
    SV-95405r1_rule EX16-MB-000460 CCI-001095 LOW The Exchange Outbound Connection Timeout must be 10 minutes or less. Email system availability depends in part on best practice 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
    SV-95407r1_rule EX16-MB-000470 CCI-001308 MEDIUM Exchange Internal Receive connectors must not allow anonymous connections. 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), it will n
    SV-95409r1_rule EX16-MB-000480 CCI-001308 MEDIUM Exchange external/Internet-bound automated response messages must be disabled. Spam originators, in an effort to refine mailing lists, sometimes monitor transmissions for automated bounce-back messages. Automated messages include such items as "Out of Office" responses, nondelivery messages, and automated message forwarding. Automa
    SV-95411r1_rule EX16-MB-000490 CCI-001308 MEDIUM Exchange must have anti-spam filtering installed. Originators of spam messages are constantly changing their techniques in order to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. A manual update procedure is labor intensive and does not sc
    SV-95413r1_rule EX16-MB-000500 CCI-001308 MEDIUM Exchange must have anti-spam filtering enabled. Originators of spam messages are constantly changing their techniques in order to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. A manual update procedure is labor intensive and does not sc
    SV-95415r1_rule EX16-MB-000510 CCI-001308 MEDIUM Exchange must have anti-spam filtering configured. Originators of spam messages are constantly changing their techniques in order to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. A manual update procedure is labor intensive and does not sc
    SV-95419r1_rule EX16-MB-000530 CCI-001308 HIGH Exchange servers must have an approved DoD email-aware virus protection software installed. With the proliferation of trojans, viruses, and spam attaching themselves to email messages (or attachments), it is necessary to have capable email-aware anti-virus (AV) products to scan messages and identify any resident malware. Because email messages a
    SV-95421r1_rule EX16-MB-000540 CCI-001308 LOW The Exchange Global Recipient Count Limit must be set. Email system availability depends in part on best practice 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 se
    SV-95423r1_rule EX16-MB-000550 CCI-002361 LOW The Exchange Receive connector timeout must be limited. Email system availability depends in part on best practice 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.
    SV-95425r1_rule EX16-MB-000570 CCI-001812 MEDIUM The Exchange application directory must be protected from unauthorized access. 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 w
    SV-95427r1_rule EX16-MB-002930 CCI-000213 MEDIUM Exchange must have authenticated access set to Integrated Windows Authentication only. To mitigate the risk of unauthorized access to sensitive information by entities that have been issued certificates by DoD-approved PKIs, all DoD systems (e.g., networks, web servers, and web portals) must be properly configured to incorporate access cont
    SV-95429r1_rule EX16-MB-002920 CCI-000068 MEDIUM Exchange must have Forms-based Authentication enabled. Identification and Authentication provide the foundation for access control. Access to email services applications in the DoD requires authentication using DoD Public Key Infrastructure (PKI) certificates. Authentication for Outlook Web App (OWA) is used
    SV-95431r1_rule EX16-MB-002910 CCI-000068 MEDIUM Exchange must use encryption for Outlook Web App (OWA) access. This setting controls whether client machines should be forced to use secure channels to communicate with this virtual directory. If this feature is enabled, clients will only be able to communicate with the directory if they are capable of supporting sec
    SV-95433r1_rule EX16-MB-002900 CCI-000068 MEDIUM Exchange must use encryption for RPC client access. This setting controls whether client machines are forced to use secure channels to communicate with the server. If this feature is enabled, clients will only be able to communicate with the server over secure communication channels. Failure to require se
    SV-95435r1_rule EX16-MB-002890 CCI-001242 MEDIUM A DoD-approved third party Exchange-aware malicious code protection application must be implemented. Malicious code protection mechanisms include but are not limited to anti-virus and malware detection software. To minimize potential negative impact to the organization that can be caused by malicious code, it is imperative that malicious code is identifi
    SV-95437r1_rule EX16-MB-002880 CCI-001242 MEDIUM The applications built-in Malware Agent must be disabled. Malicious code protection mechanisms include but are not limited to anti-virus and malware detection software. To minimize potential negative impact to the organization that can be caused by malicious code, it is imperative that malicious code is identifi
    SV-95439r1_rule EX16-MB-000580 CCI-001813 MEDIUM An Exchange software baseline copy must exist. 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
    SV-95441r1_rule EX16-MB-000590 CCI-001814 MEDIUM Exchange software must be monitored for unauthorized changes. Monitoring software files for changes against a baseline on a regular basis may help detect the possible introduction of malicious code on a system.
    SV-95443r1_rule EX16-MB-000600 CCI-001762 MEDIUM Exchange services must be documented and unnecessary services must be removed or disabled. 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 ou
    SV-95445r1_rule EX16-MB-000610 CCI-001953 MEDIUM Exchange Outlook Anywhere clients must use NTLM authentication to access email. Identification and authentication provide the foundation for access control. Access to email services applications require NTLM authentication. Outlook Anywhere, if authorized for use by the site, must use NTLM authentication when accessing email. Note:
    SV-95447r1_rule EX16-MB-000620 CCI-002530 MEDIUM The Exchange Email application must not share a partition with another application. 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 ot
    SV-95449r1_rule EX16-MB-002870 CCI-000366 MEDIUM The application must be configured in accordance with the security configuration settings based on DoD security configuration or implementation guidance, including STIGs, NSA configuration guides, CTOs, and DTMs. Configuring the application to implement organization-wide security implementation guides and security checklists ensures compliance with Federal standards and establishes a common security baseline across DoD that reflects the most restrictive security p
    SV-95451r1_rule EX16-MB-000680 CCI-002605 MEDIUM Exchange must have the most current, approved service pack installed. Failure to install the most current Exchange service pack leaves a system vulnerable to exploitation. Current service packs correct known security and system vulnerabilities.
    SV-95453r1_rule EX16-MB-000670 CCI-002385 MEDIUM Exchange must provide Mailbox databases in a highly available and redundant configuration. Exchange Server mailbox databases and any data contained in those mailboxes should be protected. This can be accomplished by configuring Mailbox servers and databases for high availability and site resilience. A database availability group (DAG) is a c
    SV-95455r1_rule EX16-MB-000630 CCI-002385 MEDIUM Exchange must not send delivery reports to remote domains. 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
    SV-95457r1_rule EX16-MB-000640 CCI-002385 MEDIUM Exchange must not send nondelivery reports to remote domains. 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 nondelivery reports to remote domains are disabled. Befo
    SV-95459r1_rule EX16-MB-000650 CCI-002385 MEDIUM The Exchange SMTP automated banner response must not reveal server details. 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 and stating the name, release level, and (often) additional information
    SV-95461r1_rule EX16-MB-000660 CCI-002385 MEDIUM Exchange Internal Send connectors must use an authentication level. The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal servers. This setting controls the encryption method used for co