The network device must log all interface access control lists (ACL) deny statements.
Auditing and logging are key components of any security architecture. It is essential for security personnel to know what is being done, attempted to be done, and by whom in order to compile an accurate risk assessment. Auditing the actions on network devices provides a means to recreate an attack, or identify a configuration mistake on the device.Information Assurance OfficerECAT-1, ECAT-2, ECSC-1
The IAO/NSO will ensure that workstation clients’ real IPv4 addresses are not revealed to the public by implementing NAT on the firewall or the router.
NAT works well with the implementation of RFC 1918 addressing scheme, it also has the privacy benefit of hiding real internal addresses. An attacker can learn more about a site’s private network once it has discovered the real IP addresses of the hosts within.Information Assurance OfficerEBBD-1, EBBD-2, EBBD-3, ECSC-1
The IAO will ensure IPSec VPNs are established as tunnel type VPNs when transporting management traffic across an ip backbone network.
Using dedicated paths, the OOBM backbone connects the OOBM gateway routers located at the premise of the managed networks and at the NOC. Dedicated links can be deployed using provisioned circuits (ATM, Frame Relay, SONET, T-carrier, and others or VPN technologies such as subscribing to MPLS Layer 2 and Layer 3 VPN services) or implementing a secured path with gateway-to-gateway IPsec tunnel. The tunnel mode ensures that the management traffic will be logically separated from any other traffic traversing the same path.Information Assurance OfficerEBVC-1, ECSC-1
Network devices must be password protected.
Network access control mechanisms interoperate to prevent unauthorized access and to enforce the organization's security policy. Access to the network must be categorized as administrator, user, or guest so the appropriate authorization can be assigned to the user requesting access to the network or a network device. Authorization requires an individual account identifier that has been approved, assigned, and configured on an authentication server. Authentication of user identities is accomplished through the use of passwords, tokens, biometrics, or in the case of multi-factor authentication, some combination thereof. Lack of authentication enables anyone to gain access to the network or possibly a network device providing opportunity for intruders to compromise resources within the network infrastructure.Information Assurance OfficerECSC-1, IAIA-1, IAIA-2
Network devices must display the DoD-approved logon banner warning.
All network devices must present a DoD-approved warning banner prior to a system administrator logging on. The banner should warn any unauthorized user not to proceed. It also should provide clear and unequivocal notice to both authorized and unauthorized personnel that access to the device is subject to monitoring to detect unauthorized usage. Failure to display the required logon warning banner prior to logon attempts will limit DoD's ability to prosecute unauthorized access and also presents the potential to give rise to criminal and civil liability for systems administrators and information systems managers. In addition, DISA's ability to monitor the device's usage is limited unless a proper warning banner is displayed.
DoD CIO has issued new, mandatory policy standardizing the wording of "notice and consent" banners and matching user agreements for all Secret and below DoD information systems, including stand-alone systems by releasing DoD CIO Memo, "Policy on Use of Department of Defense (DoD) Information Systems Standard Consent Banner and User Agreement", dated 9 May 2008. The banner is mandatory and deviations are not permitted except as authorized in writing by the Deputy Assistant Secretary of Defense for Information and Identity Assurance. Implementation of this banner verbiage is further directed to all DoD components for all DoD assets via USCYBERCOM CTO 08-008A.Information Assurance OfficerECWM-1
The network devices must timeout management connections for administrative access after 10 minutes or less of inactivity.
Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled between the managed network device and a PC or terminal server when the later has been left unattended. In addition quickly terminating an idle session will also free up resources committed by the managed network device as well as reduce the risk of a management session from being hijacked. Setting the timeout of the session to 10 minutes or less increases the level of protection afforded critical network components.Information Assurance OfficerECSC-1
Network devices must have DNS servers defined if it is configured as a client resolver.
The susceptibility of IP addresses to spoofing translates to DNS host name and IP address mapping vulnerabilities. For example, suppose a source host wishes to establish a connection with a destination host and queries a DNS server for the IP address of the destination host name. If the response to this query is the IP address of a host operated by an attacker, the source host will establish a connection with the attacker's host, rather than the intended target. The user on the source host might then provide logon, authentication, and other sensitive data.Information Assurance OfficerECSC-1
Network devices must only allow SNMP access from addresses belonging to the management network.
Detailed information about the network is sent across the network via SNMP. If this information is discovered by attackers it could be used to trace the network, show the networks topology, and possibly gain access to network devices.Information Assurance OfficerECSC-1
The network device must use different SNMP community names or groups for various levels of read and write access.
Numerous vulnerabilities exist with SNMP; therefore, without unique SNMP community names, the risk of compromise is dramatically increased. This is especially true with vendors default community names which are widely known by hackers and other networking experts. If a hacker gains access to these devices and can easily guess the name, this could result in denial of service, interception of sensitive information, or other destructive actions.Information Assurance OfficerECSC-1
The firewall must not utilize any services or capabilities other than firewall software (e.g., DNS servers, e-mail client servers, ftp servers, web servers, etc.), and if these services are part of the standard firewall suite, they will be either uninstalled or disabled.
The more services that the firewall has enabled increases the risk for an attack since the firewall will listen for these services.Information Assurance OfficerECSC-1
Group accounts must not be configured for use on the network device.
Group accounts configured for use on a network device do not allow for accountability or repudiation of individuals using the shared account. If group accounts are not changed when someone leaves the group, that person could possibly gain control of the network device. Having group accounts does not allow for proper auditing of who is accessing or changing the network.Information Assurance OfficerIAIA-1, IAIA-2
Authorized accounts must be assigned the least privilege level necessary to perform assigned duties.
By not restricting authorized accounts to their proper privilege level, access to restricted functions may be allowed before authorized personnel are trained or experienced enough to use those functions. Network disruptions or outages may occur due to mistakes made by inexperienced persons using accounts with greater privileges than necessary.Information Assurance OfficerECSC-1
Unauthorized accounts must not be configured for access to the network device.
A malicious user attempting to gain access to the network device may compromise an account that may be unauthorized for use. The unauthorized account may be a temporary or inactive account that is no longer needed to access the device. Denial of Service, interception of sensitive information, or other destructive actions could potentially take place if an unauthorized account is configured to access the network device.Information Assurance OfficerECSC-1, IAAC-1
Network devices must be configured to ensure passwords are not viewable when displaying configuration information.
Many attacks on information systems and network devices are launched from within the network. Hence, it is imperative that all passwords are encrypted so they cannot be intercepted by viewing the console or printout of the configuration.Information Assurance OfficerECSC-1
Management connections to a network device must be established using secure protocols with FIPS 140-2 validated cryptographic modules.
Administration and management connections performed across a network are inherently dangerous because anyone with a packet sniffer and access to the right LAN segment can acquire the network device account and password information. With this intercepted information they could gain access to the router and cause denial of service attacks, intercept sensitive information, or perform other destructive actions.Information Assurance OfficerDCNR-1, ECSC-1
Network devices must log all attempts to establish a management connection for administrative access.
Audit logs are necessary to provide a trail of evidence in case the network is compromised. Without an audit trail that provides a when, where, who and how set of information, repeat offenders could continue attacks against the network indefinitely. With this information, the network administrator can devise ways to block the attack and possibly identify and prosecute the attacker.Information Assurance OfficerECAT-1, ECAT-2
Network devices must have HTTP service for administrative access disabled.
The additional services that the router is enabled for increases the risk for an attack since the router will listen for these services. In addition, these services provide an unsecured method for an attacker to gain access to the router. Most recent software versions support remote configuration and monitoring using the World Wide Web's HTTP protocol. In general, HTTP access is equivalent to interactive access to the router. The authentication protocol used for HTTP is equivalent to sending a clear-text password across the network, and, unfortunately, there is no effective provision in HTTP for challenge-based or one-time passwords. This makes HTTP a relatively risky choice for use across the public Internet. Any additional services that are enabled increase the risk for an attack since the router will listen for these services.Information Assurance OfficerECSC-1
Network devices must not have any default manufacturer passwords.
Network devices not protected with strong password schemes provide the opportunity for anyone to crack the password thus gaining access to the device and causing network outage or denial of service. Many default vendor passwords are well-known; hence, not removing them prior to deploying the network devices into production provides an opportunity for a malicious user to gain unauthorized access to the device.Information Assurance OfficerECSC-1
The device must be configured to protect the network against denial of service attacks such as Ping of Death, TCP SYN floods, etc.
A SYN-flood attack is a denial-of-service attack where the attacker sends a huge amount of please-start-a-connection packets and then nothing else. This causes the device being attacked to be overloaded with the open sessions and eventually crash.
A ping sweep (also known as an ICMP sweep) is a basic network scanning technique used to determine which of a range of IP addresses map to live hosts (computers).Information Assurance OfficerEBBD-1, EBBD-2, EBBD-3, ECSC-1
Network devices must be running a current and supported operating system with all IAVMs addressed.
Network devices not running the latest tested and approved versions of software are vulnerable to network attacks. Running the most current, approved version of system and device software helps the site maintain a stable base of security fixes and patches, as well as enhancements to IP security. Viruses, denial of service attacks, system weaknesses, back doors and other potentially harmful situations could render a system vulnerable, allowing unauthorized access to DoD assets.Information Assurance OfficerECSC-1
The network device must require authentication prior to establishing a management connection for administrative access.
Network devices with no password for administrative access via a management connection provide the opportunity for anyone with network access to the device to make configuration changes enabling them to disrupt network operations resulting in a network outage.Information Assurance OfficerECSC-1
The network devices must be configured to alert the administrator of a potential attack or system failure.
The IDS or firewall is the first device that is under the sites control that has the possibility to alarm the local staff of an ongoing attack. An alert from either of these devices can be the first indication of an attack or system failure.Information Assurance OfficerECAT-2, ECSC-1
Administrator logons, changes to the administrator group, and account lockouts must be logged.
The network device and the associated logging functions allows for forensic investigations if properly configured and protected. The administrators account is the most sought after account so extra protection must be taken to protect this account and log its activity.Information Assurance OfficerECAR-1, ECAR-2, ECAR-3, ECSC-1
The network device must use SNMP Version 3 Security Model with FIPS 140-2 validated cryptography for any SNMP agent configured on the device.
SNMP Versions 1 and 2 are not considered secure. Without the strong authentication and privacy that is provided by the SNMP Version 3 User-based Security Model (USM), an unauthorized user can gain access to network management information used to launch an attack against the network.Information Assurance OfficerECSC-1
The network device must not use the default or well-known SNMP community strings public and private.
Network devices may be distributed by the vendor pre-configured with an SNMP agent using the well-known SNMP community strings public for read only and private for read and write authorization. An attacker can obtain information about a network device using the read community string "public". In addition, an attacker can change a system configuration using the write community string "private".Information Assurance OfficerECSC-1, IAIA-1, IAIA-2
In the event the authentication server is down or unavailable, there must only be one local account of last resort created for emergency use.
Authentication for administrative access to the device is required at all times. A single account of last resort can be created on the device's local database for use in an emergency such as when the authentication server is down or connectivity between the device and the authentication server is not operable. The console or account of last resort logon credentials must be stored in a sealed envelope and kept in a safe.ECSC-1
The network devices must time out access to the console port at 10 minutes or less of inactivity.
Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition quickly terminating an idle session will also free up resources committed by the managed network device. Setting the timeout of the session to 10 minutes or less increases the level of protection afforded critical network components.Information Assurance OfficerECSC-1
Network devices must only allow SNMP read-only access.
Enabling write access to the device via SNMP provides a mechanism that can be exploited by an attacker to set configuration variables that can disrupt network operations.Information Assurance OfficerECSC-1
L2TP must not pass into the private network of an enclave.
Unlike GRE (a simple encapsulating header) L2TP is a full-fledged communications protocol with control channel, data channels, and a robust command structure. In addition to PPP, other link layer types (called pseudowires) can be and are defined for delivery in L2TP by separate RFC documents. Further complexity is created by the capability to define vender-specific parameters beyond those defined in the L2TP specifications.
The endpoint devices of an L2TP connection can be an L2TP Access Concentrator (LAC) in which case it inputs/outputs the layer 2 protocol to/from the L2TP tunnel. Otherwise it is an L2TP Network Server (LNS), in which case it inputs/outputs the layer 3 (IP) protocol to/from the L2TP tunnel. The specifications describe three reference models: LAC-LNS, LAC-LAC, and LNS-LNS, the first of which is the most common case. The LAC-LNS model allows a remote access user to reach his home network or ISP from a remote location. The remote access user either dials (or otherwise connects via layer 2) to a LAC device which tunnels his connection home to an awaiting LNS. The LAC could also be located on the remote user's laptop which connects to an LNS at home using some generic internet connection. The other reference models may be used for more obscure scenarios.
Although the L2TP protocol does not contain encryption capability, it can be operated over IPSEC which would provide authentication and confidentiality. A remote user in the LAC-LNS model would most likely obtain a dynamically assigned IP address from the home network to ultimately use through the tunnel back to the home network. Secondly, the outer IP source address used to send the L2TP tunnel packet to the home network is likely to be unknown or highly variable. Thirdly, since the LNS provides the remote user with a dynamic IP address to use, the firewall at the home network would have to be dynamically updated to accept this address in conjunction with the outer tunnel address. Finally, there is also the issue of authentication of the remote user prior to divulging an acceptable IP address. As a result of all of these complications, the strict filtering rules applied to the IP-in-IP and GRE tunneling cases will likely not be possible in the L2TP scenario.
In addition to the difficulty of enforcing addresses and endpoints (as explained above), the L2TP protocol itself is a security concern if allowed through a security boundary. In particular:
1) L2TP potentially allows link layer protocols to be delivered from afar. These protocols were intended for link-local scope only, are less defended, and not as well-known
2) The L2TP tunnels can carry IP packets that are very difficult to see and filter because of the additional layer 2 overhead
3) L2TP is highly complex and variable (vender-specific variability) and therefore would be a viable target that is difficult to defend. It is better left outside of the main firewall where less damage occurs if the L2TP-processing node is compromised.
4) Filtering cannot be used to detect and prevent other unintended layer 2 protocols from being tunneled. The strength of the application layer code would have to be relied on to achieve this task.
5) Regardless of whether the L2TP is handled inside or outside of the main network, a secondary layer of IP filtering is required, therefore bringing it inside doesn't save resources.
Therefore, it is not recommended to allow unencrypted L2TP packets across the security boundary into the network's protected areas. Reference the Backbone Transport STIG for additional L2TP guidance and use.Information Assurance OfficerECSC-1
The network device must require authentication for console access.
Network devices with no password for administrative access via the console provide the opportunity for anyone with physical access to the device to make configuration changes enabling them to disrupt network operations resulting in a network outage.Information Assurance OfficerIAIA-1, IAIA-2
The FA will ensure that if the firewall product operates on an OS platform, the host must be STIG compliant prior to the installation of the firewall product.
If the host that a firewall engine is operating on is not secured, the firewall itself is exposed to greater risk.Information Assurance OfficerDCCS-1, DCCS-2, ECSC-1
The network devices must only allow management connections for administrative access from hosts residing in the management network.
Remote administration is inherently dangerous because anyone with a sniffer and access to the right LAN segment could acquire the device account and password information. With this intercepted information they could gain access to the infrastructure and cause denial of service attacks, intercept sensitive information, or perform other destructive actions.Information Assurance OfficerECSC-1
The network devices must be configured to timeout after 60 seconds or less for incomplete or broken SSH sessions.
An attacker may attempt to connect to the device using SSH by guessing the authentication method, encryption algorithm, and keys. Limiting the amount of time allowed for authenticating and negotiating the SSH session reduces the window of opportunity for the malicious user attempting to make a connection to the network device.Information Assurance OfficerECSC-1
The network device must be configured for a maximum number of unsuccessful SSH logon attempts set at 3 before resetting the interface.
An attacker may attempt to connect to the device using SSH by guessing the authentication method and authentication key or shared secret. Setting the authentication retry to 3 or less strengthens against a Brute Force attack.Information Assurance OfficerECSC-1
The network device must drop half-open TCP connections through filtering thresholds or timeout periods.
A TCP connection consists of a three-way handshake message sequence. A connection request is transmitted by the originator, an acknowledgement is returned from the receiver, and then an acceptance of that acknowledgement is sent by the originator.
An attacker's goal in this scenario is to cause a denial of service to the network or device by initiating a high volume of TCP packets, then never sending an acknowledgement, leaving connections in a half-opened state. Without the device having a connection or time threshold for these half-opened sessions, the device risks being a victim of a denial of service attack. Setting a TCP timeout threshold will instruct the device to shut down any incomplete connections. Services such as SSH, BGP, SNMP, LDP, etc. are some services that may be prone to these types of denial of service attacks. If the router does not have any BGP connections with BGP neighbors across WAN links, values could be set to even tighter constraints.Information Assurance OfficerECSC-1
The SA will utilize ingress and egress ACLs to restrict traffic destined to the enclave perimeter in accordance with the guidelines contained in DoD Instruction 8551.1 for all ports and protocols required for operational commitments.
Vulnerability assessments must be reviewed by the SA and protocols must be approved by the IA staff before entering the enclave.
Access Control Lists (ACLs) are the first line of defense in a layered security approach. They permit authorized packets and deny unauthorized packets based on port or service type. They enhance the posture of the network by not allowing packets to even reach a potential target within the security domain. The list provided are highly susceptible ports and services that should be blocked or limited as much as possible without adversely affecting customer requirements. Auditing packets attempting to penetrate the network but are stopped by an ACL will allow network administrators to broaden their protective ring and more tightly define the scope of operation.
If the perimeter is in a Deny-by-Default posture and what is allowed through the filter is IAW DoD Instruction 8551.1, and if the permit rule is explicitly defined with explicit ports and protocols allowed, then all requirements related to PPS being blocked would be satisfied.
Information Assurance OfficerECSC-1
The auxiliary port must be disabled unless it is connected to a secured modem providing encryption and authentication.
The use of POTS lines to modems connecting to network devices provides clear text of authentication traffic over commercial circuits that could be captured and used to compromise the network. Additional war dial attacks on the device could degrade the device and the production network.
Secured modem devices must be able to authenticate users and must negotiate a key exchange before full encryption takes place. The modem will provide full encryption capability (Triple DES) or stronger. The technician who manages these devices will be authenticated using a key fob and granted access to the appropriate maintenance port, thus the technician will gain access to the managed device (router, switch, etc.). The token provides a method of strong (two-factor) user authentication. The token works in conjunction with a server to generate one-time user passwords that will change values at second intervals. The user must know a personal identification number (PIN) and possess the token to be allowed access to the device.Information Assurance OfficerECSC-1
Router advertisements must be suppressed on all external-facing IPv6-enabled interfaces.
Many of the known attacks in stateless autoconfiguration are defined in RFC 3756 were present in IPv4 ARP attacks. IPSec AH was originally suggested as mitigation for the link local attacks, but has since been found to have bootstrapping problems and to be very administrative intensive. Due to first requiring an IP address in order to set up the IPSec security association creates the chicken-before-the-egg dilemma. There are solutions being developed (Secure Neighbor Discovery and Cryptographic Generated Addressing) to secure these threats but are not currently available at the time of this writing.
To mitigate these vulnerabilities, links that have no hosts connected such as the interface connecting to external gateways will be configured to suppress router advertisements.
Disable (or do not configure) all IPv6 Neighbor Discovery functions across tunnels including the Neighbor Unreachability Detection (NUD) function. Note: this is applicable only when the inner IP layer is IPv6 since IPv4 does not have the Neighbor Discovery functionality.Information Assurance OfficerDCBP-1, ECSC-1
The SA must configure the firewall for the minimum content and protocol inspection requirements.
Creating a filter to allow a port or service through the firewall without content or protocol inspection creates a direct connection between the host in the private network and a host on the outside; thereby, bypassing additional security measures that could be provided. This places the internal host at a greater risk of exploitation that could make the entire network vulnerable to an attack.DCCS-2, ECSC-1
The firewall must reject requests for access or services where the source address received by the firewall specifies a loopback address.
The loopback address is used by an Inter-Processor Control (IPC) mechanism that enables the client and server portion of an application running on the same machine to communicate, and so it is trusted. It should never be used as the source IP address of an inbound or outbound transmission.Information Assurance OfficerECSC-1
Alerts must be automatically generated to notify the administrator when log storage reaches seventy-five percent or more of its maximum capacity.
Configuring the network device or syslog server to provide alerts to the administrator in the event of modification or audit log capacity being exceeded ensures administrative staff is aware of critical alerts. Without this type of notification setup, logged audits and events could potentially fill to capacity, causing subsequent records to not be recorded and dropped without any knowledge by the administrative staff. Other unintended consequences of filling the log storage to capacity may include a denial of service of the device itself without proper notification.Information Assurance OfficerECSC-1
The network device must dump logs when they reach 75% capacity to a syslog server.
Having a procedure tested and verified will prevent the logs from filling when they reach 75% capacity.ECSC-1
Critical alerts must be generated and notifications sent to authorized personnel regardless if the person is logged in.
By immediately displaying an alarm message, identifying the potential security violation and making it accessible with the audit record contents associated with the event(s) that generated the alarm provides the administration staff prompt alert messages, regardless if the person is logged into the system.Information Assurance OfficerECAR-1, ECAR-2, ECAR-3, ECSC-1
The ISSO must ensure the message is displayed at the remote console if an administrator is already logged in, or when an administrator logs in if the alarm message has not been acknowledged.
By immediately displaying an alarm message, identifying the potential security violation and making it accessible with the audit record contents associated with the auditable event(s) that generated the alarm provides the administration staff prompt alert messages at their work areas.Information Assurance OfficerECAR-1, ECAR-2, ECAR-3, ECSC-1
The ISSO must ensure the alarm message identifying the potential security violation makes accessible the audit record contents associated with the event(s).
The relevant audit information must be available to administrators. The firewall shall immediately display an alarm message, identifying the potential security violation and make accessible the audit record contents associated with the event(s) that generated the alarm.Information Assurance OfficerECAR-1, ECAR-2, ECAR-3, ECSC-1
The ISSO must ensure an alert will remain written on the consoles until acknowledged by an administrator.
Critical alerts require immediate response. Critical alerts must not roll off the screens. The requirements are necessary to ensure an administrator will be aware of the alerts or alarm. The intent is to ensure that if an administrator is physically at the remote workstation the message will remain displayed until they have acknowledged it.Information Assurance OfficerECAR-1, ECAR-2, ECAR-3, ECSC-1
The ISSO must ensure an acknowledgement message identifying a reference to the potential security violation is logged and it contains a notice that it has been acknowledged, the time of the acknowledgement and the user identifier that acknowledged the alarm, at the remote administrator session that received the alarm.
Acknowledging the alert could be a single event, or different events. In addition, assurance is required that each administrator that received the alarm message also receives the acknowledgement message, which includes some form of reference to the alarm message, who acknowledged the message and when.Information Assurance OfficerECAR-1, ECAR-2, ECAR-3, ECSC-1
Network devices must be configured with rotating keys used for authenticating IGP peers that have a duration exceeding 180 days.
If the keys used for routing protocol authentication are guessed, the malicious user could create havoc within the network by advertising incorrect routes and redirecting traffic. Changing the keys frequently reduces the risk of them eventually being guessed. When configuring authentication for routing protocols that provide key chains, configure two rotating keys with overlapping expiration dates, both with 180-day expirations.Information Assurance OfficerIAKM-1, IAKM-2, IAKM-3
Network devices must authenticate all NTP messages received from NTP servers and peers.
Since NTP is used to ensure accurate log file timestamp information, NTP could pose a security risk if a malicious user were able to falsify NTP information. To launch an attack on the NTP infrastructure, a hacker could inject time that would be accepted by NTP clients by spoofing the IP address of a valid NTP server. To mitigate this risk, the time messages must be authenticated by the client before accepting them as a time source.
Two NTP-enabled devices can communicate in either client-server mode or peer-to-peer mode (aka "symmetric mode"). The peering mode is configured manually on the device and indicated in the outgoing NTP packets. The fundamental difference is the synchronization behavior: an NTP server can synchronize to a peer with better stratum, whereas it will never synchronize to its client regardless of the client's stratum. From a protocol perspective, NTP clients are no different from the NTP servers. The NTP client can synchronize to multiple NTP servers, select the best server and synchronize with it, or synchronize to the averaged value returned by the servers.
A hierarchical model can be used to improve scalability. With this implementation, an NTP client can also become an NTP server providing time to downstream clients at a higher stratum level and of decreasing accuracy than that of its upstream server. To increase availability, NTP peering can be used between NTP servers. In the event the device loses connectivity to it upstream NTP server, it will be able to choose time from one of its peers.
The NTP authentication model is opposite of the typical client-server authentication model. NTP authentication enables an NTP client or peer to authenticate time received from their servers and peers. It's not used to authenticate NTP clients because NTP servers don't care about the authenticity of their clients, as they never accept any time from them.Information Assurance OfficerECSC-1
The network device must be configured to ensure IPv6 Site Local Unicast addresses are not defined in the enclave, (FEC0::/10). Note that this consist of all addresses that begin with FEC, FED, FEE and FEF.
As currently defined, site local addresses are ambiguous and can be present in multiple sites. The address itself does not contain any indication of the site to which it belongs. The use of site-local addresses has the potential to adversely affect network security through leaks, ambiguity and potential misrouting, as documented in section 2 of RFC3879. RFC3879 formally deprecates the IPv6 site-local unicast prefix defined in RFC3513, i.e., 1111111011 binary or FEC0::/10.Information Assurance OfficerECSC-1
The network device must not allow SSH Version 1 to be used for administrative access.
SSH Version 1 is a protocol that has never been defined in a standard. Since SSH-1 has inherent design flaws which make it vulnerable to attacks, e.g., man-in-the-middle attacks, it is now generally considered obsolete and should be avoided by explicitly disabling fallback to SSH-1.Information Assurance OfficerECSC-1
Teredo packets must be blocked inbound to the enclave and outbound from the enclave.
Teredo (RFC 4380) is a tunneling mechanism that allows computers to encapsulate IPv6 packets inside IPv4 to traverse IPv4-only networks. It relies on UDP to allow the tunnel to traverse NAT devices. Teredo uses UDP port 3544 to communicate with Teredo relays which access the packet, decapsulated the packet, and route it to the appropriate IPv6 network. While Teredo was proposed by Microsoft, Linux versions do exist.
By allowing Teredo tunneling mechanism to be uncontrolled, it can pass malicious IPv6 packets over IPv4 without further inspection of the packet by router and firewall ACLs.Information Assurance OfficerECSC-1
Interfaces supporting IPv4 in NAT-PT Architecture must not receive IPv6 traffic.
Network Address Translation with Protocol Translation (NAT-PT), defined in [RFC2766], is a service that can be used to translate data sent between IP-heterogeneous nodes. NAT-PT translates IPv4 datagrams into a semantically equivalent IPv6 datagram or vice versa. For this service to work it has to be located in the connection point between the IPv4 network and the IPv6 network. The PT-part of the NAT-PT handles the interpretation and translation of the semantically equivalent IP header, either from IPv4 to IPv6 or from IPv6 to IPv4. Like NAT, NATPT also uses a pool of addresses which it dynamically assigns to the translated datagrams.
The NAT-PT architecture is not one of the preferred DoD IPv6 transition paradigms due to the deprecation of NAT-PT within the DoD community. However, as described in the "DoD IPv6 Guidance for Information Assurance (IA) Milestone Objective 3 (MO3) Requirements, some services/agencies may choose to implement this transition mechanism within an enclave. The following sub-sections provide guidelines for the use of NAT-PT within a controlled enclave.
In addition to the single point of failure, the reduced performance of an application level gateway, coupled with limitations on the kinds of applications that work, decreases the overall value and utility of the network. NAT-PT also inhibits the ability to deploy security at the IP layer.Information Assurance OfficerECSC-1
Network devices must use two or more authentication servers for the purpose of granting administrative access.
The use of Authentication, Authorization, and Accounting (AAA) affords the best methods for controlling user access, authorization levels, and activity logging. By enabling AAA on the routers in conjunction with an authentication server such as TACACS+ or RADIUS, the administrators can easily add or remove user accounts, add or remove command authorizations, and maintain a log of user activity.
The use of an authentication server provides the capability to assign router administrators to tiered groups that contain their privilege level that is used for authorization of specific commands. For example, user mode would be authorized for all authenticated administrators while configuration or edit mode should only be granted to those administrators that are permitted to implement router configuration changes.Information Assurance OfficerIAIA-1
The emergency account must be set to an appropriate authorization level to perform necessary administrative functions when the authentication server is not online.
The emergency account is to be configured as a local account on the network devices. It is to be used only when the authentication server is offline or not reachable via the network. The emergency account must be set to an appropriate authorization level to perform necessary administrative functions during this time.Information Assurance OfficerECSC-1
Management traffic is not restricted to only the authorized management packets based on destination and source IP address.
The Out-of-Band Management (OOBM) network is an IP network used exclusively for the transport of OAM&P data from the network being managed to the OSS components located at the NOC. Its design provides connectivity to each managed network element enabling network management traffic to flow between the managed NEs and the NOC. This allows the use of paths separate from those used by the network being managed. Traffic from the managed network to the management network and vice-versa must be secured via IPSec encapsulation. Information Assurance OfficerECNK-1
Gateway configuration at the remote VPN end-point is a not a mirror of the local gateway
The IPSec tunnel end points may be configured on the OOBM gateway routers connecting the managed network and the NOC. They may also be configured on a firewall or VPN concentrator located behind the gateway router. In either case, the crypto access-list used to identify the traffic to be protected must be a mirror (both IP source and destination address) of the crypto access list configured at the remote VPN peer.Information Assurance OfficerSystem AdministratorECSC-1
The network devices OOBM interface must be configured with an OOBM network address.
The OOBM access switch will connect to the management interface of the managed network device. The management interface of the managed network device will be directly connected to the OOBM network. An OOBM interface does not forward transit traffic; thereby, providing complete separation of production and management traffic. Since all management traffic is immediately forwarded into the management network, it is not exposed to possible tampering. The separation also ensures that congestion or failures in the managed network do not affect the management of the device. If the OOBM interface does not have an IP address from the managed network address space, it will not have reachability from the NOC using scalable and normal control plane and forwarding mechanisms.System AdministratorInformation Assurance OfficerECSC-1
The network devices management interface must be configured with both an ingress and egress ACL.
The OOBM access switch will connect to the management interface of the managed network device. The management interface can be a true OOBM interface or a standard interface functioning as the management interface. In either case, the management interface of the managed network device will be directly connected to the OOBM network.
An OOBM interface does not forward transit traffic; thereby, providing complete separation of production and management traffic. Since all management traffic is immediately forwarded into the management network, it is not exposed to possible tampering. The separation also ensures that congestion or failures in the managed network do not affect the management of the device. If the device does not have an OOBM port, the interface functioning as the management interface must be configured so that management traffic does not leak into the managed network and that production traffic does not leak into the management network.System AdministratorInformation Assurance OfficerECSC-1
The management interface must be configured as passive for the IGP instance deployed in the managed network.
The OOBM access switch will connect to the management interface of the managed network devices. The management interface can be a true OOBM interface or a standard interface functioning as the management interface. In either case, the management interface of the managed network devices will be directly connected to the OOBM network.
An OOBM interface does not forward transit traffic; thereby, providing complete separation of production and management traffic. Since all management traffic is immediately forwarded into the management network, it is not exposed to possible tampering. The separation also ensures that congestion or failures in the managed network do not affect the management of the device. If the device does not have an OOBM port, the interface functioning as the management interface must be configured so that management traffic, both data plane and control plane, does not leak into the managed network and that production traffic does not leak into the management network.System AdministratorInformation Assurance OfficerECSC-1
The firewall located behind the premise router must be configured to block all outbound management traffic.
The management network must still have its own subnet in order to enforce control and access boundaries provided by Layer 3 network nodes such as routers and firewalls. Management traffic between the managed network elements and the management network is routed via the same links and nodes as that used for production or operational traffic. Safeguards must be implemented to ensure that the management traffic does not leak past the managed network's premise equipment. If there is a firewall located behind the premise router, then all management traffic must be blocked at that point--with the exception of management traffic destined to premise equipment.System AdministratorInformation Assurance OfficerECSC-1
Traffic entering the tunnels is not restricted to only the authorized management packets based on destination address.
Similar to the OOBM model, when the production network is managed in-band, the management network could also be housed at a NOC that is located locally or remotely at a single or multiple interconnected sites. NOC interconnectivity as well as connectivity between the NOC and the managed networks’ premise routers would be enabled using either provisioned circuits or VPN technologies such as IPSec tunnels or MPLS VPN services. Information Assurance OfficerSystem AdministratorECSC-1
Server VLAN interfaces must be protected by restrictive ACLs using a deny-by-default security posture.
Protecting data sitting in a server VLAN is necessary and can be accomplished using access control lists on VLANs provisioned for servers. Without proper access control of traffic entering or leaving the server VLAN, potential threats such as a denial of service, data corruption, or theft could occur, resulting in the inability to complete mission requirements by authorized users.Information Assurance OfficerECND-1, ECSC-1
The IAO will ensure the Server Farm infrastructure is secured by ACLs on VLAN interfaces that restrict data originating from one server farm segment destined to another server farm segment.
ACLs on VLAN interfaces do not protect against compromised servers. The Server farm vlans need to protect the servers located on one subnet from servers located on another subnet. Protecting a client’s data from other clients is necessary and can be accomplished using VLAN provisioning, layer 3 filtering and content filtering at the Server Farm entry point. Restricting protocol, source and destination traffic via filters is an option; however additional security practices such as content filtering are required.
The Server farm private vlans need to protect the servers located on one subnet from servers located on another subnet.Information Assurance OfficerECND-1
The IAO will ensure the Server Farm VLANs are protected by severely restricting the actions the hosts can perform on the servers by firewall content filtering.
Most current applications are deployed as a multi-tier architecture. The multi-tier model uses separate server machines to provide the different functions of presentation, business logic, and database.
Multi-tier server farms provide added security because a compromised web server does not provide direct access to the application itself or to the database.
The multi-tier separation is accomplished in several architectures, by a layer 2 switch, by a layer3 switch/router or by a firewall located at the server farm. Using the firewall implementation is the most secure method and is the only approved DoD architecture.
Firewalls get packets from VLAN-supporting switches complete with 802.1Q tags in their headers. What the VLAN-aware firewall can do is extract the tags and use the information within the tags to make policy-based security decisions.
Information Assurance OfficerEBBD-1
IPv6 6-to-4 addresses with a prefix of 2002::/16 must be filtered at the perimeter.
"6-to-4" is a tunneling IPv6 transition mechanism [RFC 3056]. The guidance is the default case, which assumes that 6-to-4 is not being used as an IPv6 transition mechanism. If 6-to-4 is implemented, reference addition 6-to-4 guidance defined in the STIG.
Drop all inbound IPv6 packets containing a source address of type 2002::/16. This assumes the 6-to-4 transition mechanism is not being used.
Drop all inbound IPv6 packets containing a destination address of type 2002::/16. This assumes the 6-to-4 transition mechanism is not being used.Information Assurance OfficerECSC-1
IPv6 Jumbo Payload hop by hop header must be blocked.
The IPv6 Jumbo Payload allows IP packets to be larger than 65,535 bytes. This feature is only useful on very specialized high performance systems (e.g. super computers). Common place link layer technologies do not support these payload sizes and special link layer designs would be necessary. This header should be dropped unless the system is specifically designed to use very large payloads, since it only serves as an opportunity to break implementations.Information Assurance OfficerECSC-1
Network devices must use at least two NTP servers to synchronize time.
Without synchronized time, accurately correlating information between devices becomes difficult, if not impossible. If logs cannot be successfully compared between each of the routers, switches, and firewalls, it will be very difficult to determine the exact events that resulted in a network breach incident. NTP provides an efficient and scalable method for network devices to synchronize to an accurate time source.System AdministratorInformation Assurance OfficerECSC-1
The IAO will ensure that the router or firewall software has been upgraded to mitigate the risk of DNS cache poisoning attack caused by a flawed PAT implementation using a predictable source port allocation method for DNS query traffic.
DNS cache poisoning is an attack technique that allows an attacker to introduce forged DNS information into the cache of a caching name server. There are inherent deficiencies in the DNS protocol and defects in implementations that facilitate DNS cache poisoning.
Name servers vulnerable to cache poisoning attacks are due to their use of insufficiently randomized transaction IDs and UDP source ports in the DNS queries that they produce, which may allow an attacker to more easily forge DNS answers that can poison DNS caches. To exploit these vulnerabilities an attacker must be able to cause a vulnerable DNS server to perform recursive DNS queries. Therefore, DNS servers that are only authoritative, or servers where recursion is not allowed, are not affected.
The DNS protocol specification includes a transaction ID field of 16 bits. If the specification is correctly implemented and the transaction ID is randomly selected with a strong random number generator, an attacker will require, on average, 32,768 attempts to successfully predict the ID. Some flawed implementations may use a smaller number of bits for this transaction ID, meaning that fewer attempts will be needed. Furthermore, there are known errors with the randomness of transaction IDs that are generated by a number of implementations.
Some current implementations allocate an arbitrary source port at startup (and sometimes selected at random) and reuse this source port for all outgoing queries. With other implementations, the source port for outgoing queries is fixed at the traditional assigned DNS server UDP port number 53. Because attacks against these vulnerabilities all rely on an attacker's ability to predict, the implementation of per-query source port randomization in the server presents a practical mitigation against these attacks within the boundaries of the current protocol specification. Randomized source ports can be used to gain approximately 16 additional bits of randomness in the data that an attacker must guess. Randomizing the ports adds a significant amount of attack resiliency.
Routers, firewalls, proxies, and other gateway devices that perform NAT—more specifically Port Address Translation (PAT)—often rewrite source ports in order to track connection state. A flawed implementation of a PAT device using a predictiable source port allocation method can reduce any effectiveness of source port randomization implemented by name servers and stub resolvers. Henceforth, it is imperative that the router or firewall software has been upgraded or patched to reduce an attacker’s opportunity for launching a DNS cache poisoning attack.
Note: Regular NAT (allocating one public IP address for each private IP address) is not affected by this problem because it only rewrites layer 3 information and does not modify layer 4 header information of packets traversing the NAT device.
Information Assurance OfficerVIVM-1
Network device logs must be timestamped.
Device logs can be used for forensic analysis in support of incident as well as to aid with normal traffic analysis. It can take numerous days to recover from a firewall outage when a proper backup scheme is not used.Information Assurance OfficerECSC-1, ECTB-1
Network device logs must include source IP, destination IP, port, protocol used and action taken.
The network device logs can be used for forensic analysis in support of incident as well as to aid with normal traffic analysis.Information Assurance OfficerECSC-1, ECTB-1
A service or feature that calls home to the vendor must be disabled.
Call home services or features will routinely send data such as configuration and diagnostic information to the vendor for routine or emergency analysis and troubleshooting. The risk that transmission of sensitive data sent to unauthorized persons could result in data loss or downtime due to an attack.Information Assurance OfficerNetwork Security OfficerECSC-1
The IAO must ensure firewalls deployed in an IPv6 enclave meet the requirements defined by DITO and NSA milestone objective 3 guidance.
1) Drop IPv6 Undetectable protocol/port (May be an intrinsic FW feature.) - IPv6 allows an unlimited number of extension headers to be applied to a packet. A FW may not be able to locate the layer 4 protocol and port values if too many extension headers exhaust its resources. As a minimum, a FW must be able to drop any packet for which it cannot identify the layer 4 protocol and ports (if applicable). The security policy would be subverted if these packets were allowed to pass through a FW. If the FW cannot traverse through extension headers at all, it must drop packets using any extension header. This measure will disable a large amount of IPv6’s functionality and should only be used if the Primary guidance cannot be implemented.
2) Drop IPv6 Type 0 Routing Header - The IPv6 Type 0 Routing Header (extension header) is functionally equivalent to the IPv4 loose source routing header option, which is typically blocked for security reasons. The Type 0 Routing Header is dangerous because it allows attackers to spoof source addresses and get traffic in response (rather than to the real owner of the address). Secondly, a packet with an allowed destination address could be sent through a FW only to bounce to a different (disallowed) node once inside using the Routing Header functionality. If the Type 0 Routing Header must be used, it must be used in conjunction with either the IPSec AH or the IPSec Encapsulation Security Payload (ESP) headers. If the FW cannot distinguish the type field of a routing header, it should be configured to drop all routing headers. Note that Mobile IP is disabled without the Type 2 Routing Header. Although deprecated by a recent RFC, there may be existing implementations that still recognize this header.
3) Drop Undefined IPv6 Header Extensions/Protocol Values (May be an intrinsic FW feature.) - Undefined IPv6 header extensions means that the Next Header type is not registered with Internet Assigned Numbers Authority (IANA). The header extension is the same as the protocol value, and should be dropped. Drop all undefined extension headers/protocol values.
4) Drop at least one fragment of any inbound fragmented packet for which the complete data set for filtering to include protocol/port values cannot be determined.(May be an intrinsic FW feature) - A FW must be able to properly enforce its filtering policy upon fragmented packets. This requires that the FW be able to find the complete set of header data including extension headers and the upper layer protocol/port values. It also requires that the packet not be susceptible to fragment overlap attacks. Fragment overlaps are a more serious problem in IPv6 than in IPv4 because the presence of extension headers can push the upper layer protocol/port information outward (toward packet boundaries) making it much harder to protect. How a FW achieves these requirements is not important as long as both aspects are met. The wording “drop at least one fragment” used in the actions below is a statement of the bare minimum action to secure a packet, and is chosen to allow FW venders flexibility in achieving it. Refer to Firewall Design Considerations for IPv6 section 3.6 for extensive detail on this topic. https://www.us.army.mil/suite/doc/10209656
5) Drop all inbound IPv6 packets containing more than one Fragmentation Header within an IP header chain. (May be an intrinsic FW feature) - Nested fragmentation is an unnecessary and unwanted IPv6 condition that is not forbidden by the specifications. It occurs when an IP header chain contains more than one Fragmentation Header implying that a fragment has been fragmented. In the specification, the phrase “IP header chain” rather than “packet” is used, because a tunneled packet has more than one IP header chain and each chain can have a Fragment Header (this case is not nested fragmentation). Nested fragmentation is a new phenomenon with IPv6. It is not possible in IPv4, because the fragmentation fields are part of the main header and are modified in the event of a secondary fragmentation event. Nested fragmentation in IPv6 should be dropped by FWs since internal nodes that process the fragmentation may or may not be equipped to handle this unexpected case. These nodes may crash or behave in some unpredictable manner.Information Assurance OfficerDCDS-1, EBBD-1