IPSec VPN Gateway Security Technical Implementation Guide

U_Network_IPSec_VPN_Gateway_STIG_V1R15_Manual-xccdf.xml

IPSec VPN Gateway Security Technical Implementation Guide
Details

Version / Release: V1R15

Published: 2018-03-08

Updated At: 2018-09-23 19:15:34

Download

Filter

Findings
Severity Open Not Reviewed Not Applicable Not a Finding
Overall 0 0 0 0
Low 0 0 0 0
Medium 0 0 0 0
High 0 0 0 0
Drop CKL or SCAP (XCCDF) results here.
    Vuln Rule Version CCI Severity Title Description Status Finding Details Comments
    SV-3000r4_rule NET1020 LOW 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 Officer
    SV-3012r4_rule NET0230 HIGH 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 Officer
    SV-3013r4_rule NET0340 MEDIUM 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 Officer
    SV-3014r4_rule NET1639 MEDIUM 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 Officer
    SV-3020r3_rule NET0820 LOW 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 Officer
    SV-3021r3_rule NET0890 MEDIUM 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 Officer
    SV-3034r3_rule NET0400 MEDIUM Network devices must authenticate all IGP peers. A rogue router could send a fictitious routing update to convince a site's premise router to send traffic to an incorrect or even a rogue destination. This diverted traffic could be analyzed to learn confidential information of the site's network, or merely used to disrupt the network's ability to effectively communicate with other networks.Information Assurance OfficerECSC-1
    SV-3043r4_rule NET1675 MEDIUM 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 Officer
    SV-3056r7_rule NET0460 HIGH 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 Officer
    SV-3057r6_rule NET0465 MEDIUM 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 Officer
    SV-3058r5_rule NET0470 MEDIUM 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 Officer
    SV-3062r4_rule NET0600 HIGH 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 Officer
    SV-3069r5_rule NET1638 MEDIUM 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 Officer
    SV-3070r4_rule NET1640 LOW 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 Officer
    SV-3072r3_rule NET1030 LOW The running configuration must be synchronized with the startup configuration after changes have been made and implemented. If the running and startup router configurations are not synchronized properly and a router malfunctions, it will not restart with all of the recent changes incorporated. If the recent changes were security related, then the routers would be vulnerable to attack.Information Assurance Officer
    SV-3078r3_rule NET0720 LOW Network devices must have TCP and UDP small servers disabled. Cisco IOS provides the "small services" that include echo, chargen, and discard. These services, especially their User Datagram Protocol (UDP) versions, are infrequently used for legitimate purposes. However, they have been used to launch denial of service attacks that would otherwise be prevented by packet filtering. For example, an attacker might send a DNS packet, falsifying the source address to be a DNS server that would otherwise be unreachable, and falsifying the source port to be the DNS service port (port 53). If such a packet were sent to the Cisco's UDP echo port, the result would be Cisco sending a DNS packet to the server in question. No outgoing access list checks would be applied to this packet, since it would be considered locally generated by the router itself. The small services are disabled by default in Cisco IOS 12.0 and later software. In earlier software, they may be disabled using the commands no service tcp-small-servers and no service udp-small-servers.Information Assurance Officer
    SV-3079r3_rule NET0730 LOW Network devices must have the Finger service disabled. The Finger service supports the UNIX Finger protocol, which is used for querying a host about the users that are logged on. This service is not necessary for generic users. If an attacker were to find out who is using the network, they may use social engineering practices to try to elicit classified DoD information.Information Assurance Officer
    SV-3080r4_rule NET0760 MEDIUM The Configuration auto-loading feature must be disabled when connected to an operational network. Devices can find their startup configuration either in their own NVRAM or access it over the network via TFTP or Remote Copy (rcp). Loading the image from the network is taking a security risk since the image could be intercepted by an attacker who could corrupt the image resulting in a denial of service. Configuration auto-loading can be enabled when the device is connected to a non-operational network. Once the device is connected to an operational (i.e. production) network, configuration auto-loading must be disabled.
    SV-3081r3_rule NET0770 MEDIUM IP source routing must be disabled. Source routing is a feature of IP, whereby individual packets can specify routes. This feature is used in several different network attacks by bypassing perimeter and internal defense mechanisms.Information Assurance OfficerECSC-1
    SV-3083r3_rule NET0790 LOW IP directed broadcast must be disabled on all layer 3 interfaces. An IP directed broadcast is a datagram sent to the broadcast address of a subnet that is not directly attached to the sending machine. The directed broadcast is routed through the network as a unicast packet until it arrives at the target subnet, where it is converted into a link-layer broadcast. Because of the nature of the IP addressing architecture, only the last router in the chain, which is connected directly to the target subnet, can conclusively identify a directed broadcast. IP directed broadcasts are used in the extremely common and popular smurf, or Denial of Service (DoS), attacks. In a smurf attack, the attacker sends ICMP echo requests from a falsified source address to a directed broadcast address, causing all the hosts on the target subnet to send replies to the falsified source. By sending a continuous stream of such requests, the attacker can create a much larger stream of replies, which can completely inundate the host whose address is being falsified. This service should be disabled on all interfaces when not needed to prevent smurf and DoS attacks. Directed broadcast can be enabled on internal facing interfaces to support services such as Wake-On-LAN. Case scenario may also include support for legacy applications where the content server and the clients do not support multicast. The content servers send streaming data using UDP broadcast. Used in conjunction with the ip multicast helper-map feature, broadcast data can be sent across a multicast topology. The broadcast streams are converted to multicast and vice versa at the first-hop routers and last-hop routers before entering leaving the multicast transit area respectively. The last-hop router must convert the multicast to broadcast. Hence, this interface must be configured to forward a broadcast packet (i.e. a directed broadcast address is converted to the all nodes broadcast address).Information Assurance OfficerECSC-1
    SV-3085r4_rule NET0740 MEDIUM Network devices must have HTTP service for administrative access disabled. The additional services 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. The HTTPS server may be enabled for administrative access.
    SV-3086r3_rule NET0750 LOW BOOTP services must be disabled. BOOTP is a user datagram protocol (UDP) that can be used by Cisco routers to access copies of Cisco IOS Software on another Cisco router running the BOOTP service. In this scenario, one Cisco router acts as a Cisco IOS Software server that can download the software to other Cisco routers acting as BOOTP clients. In reality, this service is rarely used and can allow an attacker to download a copy of a router's Cisco IOS Software.Information Assurance Officer
    SV-3143r4_rule NET0240 HIGH 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 Officer
    SV-3160r4_rule NET0700 MEDIUM 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 Officer
    SV-3175r5_rule NET1636 HIGH 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 Officer
    SV-3196r4_rule NET1660 HIGH 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 Officer
    SV-3210r4_rule NET1665 HIGH 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 Officer
    SV-3966r6_rule NET0440 MEDIUM In the event the authentication server is unavailable, the network device must have a single local account of last resort defined. 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 local account of last resort logon credentials must be stored in a sealed envelope and kept in a safe.
    SV-3967r4_rule NET1624 MEDIUM 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 Officer
    SV-3969r5_rule NET0894 MEDIUM 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 Officer
    SV-4582r5_rule NET1623 HIGH 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 Officer
    SV-4584r3_rule NET1021 LOW The network device must log all messages except debugging and send all log data to a syslog server. Logging is a critical part of router security. Maintaining an audit trail of system activity logs (syslog) can help identify configuration errors, understand past intrusions, troubleshoot service disruptions, and react to probes and scans of the network. Syslog levels 0-6 are the levels required to collect the necessary information to help in the recovery process.Information Assurance Officer
    SV-5611r5_rule NET1637 MEDIUM 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.
    SV-5612r4_rule NET1645 MEDIUM 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 Officer
    SV-5613r4_rule NET1646 MEDIUM 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 Officer
    SV-5614r3_rule NET0722 LOW Network devices must have the PAD service disabled. Packet Assembler Disassembler (PAD) is an X.25 component seldom used. It collects the data transmissions from the terminals and gathers them into a X.25 data stream and vice versa. PAD acts like a multiplexer for the terminals. If enabled, it can render the device open to attacks. Some voice vendors use PAD on internal routers.Information Assurance Officer
    SV-5615r3_rule NET0724 LOW Network devices must have TCP Keep-Alives enabled for TCP sessions. Idle TCP sessions can be susceptible to unauthorized access and hijacking attacks. By default, routers do not continually test whether a previously connected TCP endpoint is still reachable. If one end of a TCP connection idles out or terminates abnormally, the opposite end of the connection may still believe the session is available. These "orphaned" sessions use up valuable router resources and can also be hijacked by an attacker. To mitigate this risk, routers must be configured to send periodic keepalive messages to check that the remote end of a session is still connected. If the remote device fails to respond to the keepalive message, the sending router will clear the connection and free resources allocated to the session.Information Assurance Officer
    SV-5616r3_rule NET0726 LOW Network devices must have identification support disabled. Identification support allows one to query a TCP port for identification. This feature enables an unsecured protocol to report the identity of a client initiating a TCP connection and a host responding to the connection. Identification support can connect a TCP port on a host, issue a simple text string to request information, and receive a simple text-string reply. This is another mechanism to learn the router vendor, model number, and software version being run.Information Assurance Officer
    SV-5618r3_rule NET0781 MEDIUM Gratuitous ARP must be disabled. A gratuitous ARP is an ARP broadcast in which the source and destination MAC addresses are the same. It is used to inform the network about a host IP address. A spoofed gratuitous ARP message can cause network mapping information to be stored incorrectly, causing network malfunction.Information Assurance Officer
    SV-5646r5_rule NET0965 MEDIUM 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 Officer
    SV-7365r4_rule NET1629 LOW 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 Officer
    SV-15301r4_rule NET0422 LOW Network devices must be configured with rotating keys used for authenticating IGP peers that have a duration of 180 days or less. 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 or less expirations.
    SV-15313r3_rule NET0744 MEDIUM Network devices must have BSDr commands disabled. Berkeley Software Distribution (BSD) "r" commands allow users to execute commands on remote systems using a variety of protocols. The BSD "r" commands (e.g., rsh, rlogin, rcp, rdump, rrestore, and rdist) are designed to provide convenient remote access without passwords to services such as remote command execution (rsh), remote login (rlogin), and remote file copy (rcp and rdist). The difficulty with these commands is they use address-based authentication. An attacker who convinces a server that he is coming from a "trusted" machine can essentially get complete and unrestricted access to a system. The attacker can convince the server by impersonating a trusted machine and using IP address, by confusing DNS so that DNS thinks that the attacker's IP address maps to a trusted machine's name, or by any of a number of other methods.Information Assurance Officer
    SV-15327r6_rule NET0813 MEDIUM Network devices must authenticate all NTP messages received from NTP servers and peers. Since NTP is used to ensure accurate log file time stamp 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 its 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 is not used to authenticate NTP clients because NTP servers do not care about the authenticity of their clients, as they never accept any time from them.
    SV-15336r3_rule NET0897 LOW The network device must use its loopback or OOB management interface address as the source address when originating authentication services traffic. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. TACACS+, RADIUS messages sent to management servers should use the loopback address as the source address.Information Assurance OfficerECSC-1
    SV-15339r3_rule NET0898 LOW The network device must use its loopback or OOB management interface address as the source address when originating syslog traffic. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. Syslog messages sent to management servers should use the loopback address as the source address.Information Assurance OfficerECSC-1
    SV-15342r3_rule NET0899 LOW The network device must use its loopback or OOB management interface address as the source address when originating NTP traffic. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. NTP messages sent to management servers should use the loopback address as the source address.Information Assurance OfficerECSC-1
    SV-15345r3_rule NET0900 LOW The network device must use its loopback or OOB management interface address as the source address when originating SNMP traffic. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. SNMP messages sent to management servers should use the loopback address as the source address.Information Assurance OfficerECSC-1
    SV-15348r3_rule NET0901 LOW The network device must use its loopback or OOB management interface address as the source address when originating IP Flow/NetFlow traffic. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. NetFlow messages sent to management servers should use the loopback address as the source address.Information Assurance Officer
    SV-15351r4_rule NET0902 LOW The network device must use its loopback or OOB management interface address as the source address when originating TFTP or FTP traffic. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of network devices. It is easier to construct appropriate ingress filters for management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. TFTP and FTP messages sent to management servers should use the loopback address as the source address.Information Assurance OfficerECSC-1
    SV-15357r3_rule NET0903 LOW The network device must use its loopback interface address as the source address for all iBGP peering sessions. Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability. It is easier to construct appropriate filters for control plane traffic. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses.Information Assurance Officer
    SV-15459r4_rule NET1647 MEDIUM 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 Officer
    SV-16259r4_rule NET0433 MEDIUM 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 Officer
    SV-16261r5_rule NET0441 HIGH The emergency administration account must be set to an appropriate authorization level to perform necessary administrative functions when the authentication server is not online. The emergency administration 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 Officer
    SV-19075r4_rule NET0991 MEDIUM 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 Officer
    SV-19076r4_rule NET0992 MEDIUM 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 Officer
    SV-19077r3_rule NET0993 LOW 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 Officer
    SV-21027r3_rule NET0966 MEDIUM The network device must have control plane protection enabled. The Route Processor (RP) is critical to all network operations as it is the component used to build all forwarding paths for the data plane via control plane processes. It is also instrumental with ongoing network management functions that keep the routers and links available for providing network services. Hence, any disruption to the RP or the control and management planes can result in mission critical network outages. In addition to control plane and management plane traffic that is in the router's receive path, the RP must also handle other traffic that must be punted to the RP--that is, the traffic must be fast or process switched. This is the result of packets that must be fragmented, require an ICMP response (TTL expiration, unreachable, etc.) have IP options, etc. A DoS attack targeting the RP can be perpetrated either inadvertently or maliciously involving high rates of punted traffic resulting in excessive RP CPU and memory utilization. To maintain network stability, the router must be able to securely handle specific control plane and management plane traffic that is destined to it, as well as other punted traffic. Using the ingress filter on forwarding interfaces is a method that has been used in the past to filter both forwarding path and receiving path traffic. However, this method does not scale well as the number of interfaces grows and the size of the ingress filters grow. Control plane policing can be used to increase security of routers and multilayer switches by protecting the RP from unnecessary or malicious traffic. Filtering and rate limiting the traffic flow of control plane packets can be implemented to protect routers against reconnaissance and DoS attacks allowing the control plane to maintain packet forwarding and protocol states despite an attack or heavy load on the router or multilayer switch.System AdministratorInformation Assurance OfficerECSC-1
    SV-28651r4_rule NET0812 LOW 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 Officer
    SV-40981r1_rule NET-VPN-010 HIGH The VPN gateway must use IKE for negotiating and establishing all IPSec security associations. An IPSec Security Associations (SA) is established using either Internet Key Exchange (IKE) or manual configuration. When using IKE, the security associations are established when needed and expire after a period of time or volume of traffic threshold. If manually configured, they are established as soon as the configuration is complete at both end points and they do not expire. When using IKE, the Security Parameter Index (SPI) for each security association is a pseudo-randomly derived number. Without IKE, the SPI is manually specified for each security association. IKE peers will negotiate the encryption algorithm and authentication or hashing methods as well as generate the encryption keys. With manual configuration of the IPSec security association, both the cipher key and authentication key are static. Hence, if the keys are compromised, the traffic being protected by the current IPSec tunnel can be decrypted as well as traffic in any future tunnels established by this SA. Furthermore, the peers are not authenticated prior to establishing the SA which could result in a rouge device establishing an IPSec SA with either of the VPN end points. IKE provides primary authentication to verify the identity of the remote system before negotiation begins. IKE also enables anti-replay services and will establish a lifetime for each IPSec session. These features are lost when the IPSec security associations are manually configured which results in a non-terminating session using static pre-shared keys. Information Assurance OfficerECSC-1
    SV-40983r1_rule NET-VPN-020 HIGH The VPN gateway must authenticate the remote server, peer, or client prior to establishing an IPSec session. Both IPSec endpoints must authenticate each other to ensure the identity of each by additional means besides an IP address which can easily be spoofed. The objective of IPSec is to establish a secured tunnel with privacy between the two endpoints traversing an IP backbone network. In the case of teleworkers accessing the enclave using a laptop configured with an IPSec software client, the secured path will also traverse the Internet. The secured path will grant the remote site or client access to resources within the private network; thereby establishing a level of trust. Hence, it is imperative that some form of authentication is used prior to establishing an IPSec session for transporting data to and from the enclave from a remote site.Information Assurance OfficerECSC-1
    SV-40985r1_rule NET-VPN-030 MEDIUM The VPN gateway must use PKI or digital-signature for authenticating the remote server, peer, or client. Using shared secrets between two IPSec endpoints is easy to implement but are also easy to compromise. Regardless of the strength of the password, they can be cracked using software tools that are readily available. Furthermore, implementation using shared secrets is not scalable since all VPN gateways and software clients would need to be configured with the shared secrets. In addition, there cannot be a preshared key for every user because the VPN gateway server does not know the client’s identity (the IP address is commonly used). Hence, remote users must use a group-based preshared key for authentication. When an individual leaves the group, changing the key must be coordinated with the other users of the group. PKI mitigates the risk involved with group passwords because each user has a certificate. PKI offers a scalable way to authenticate all IPSec endpoints in a secure manner. Every VPN gateway or remote client that needs to participate in IPSec VPN is issued a digital certificate by the Certification Authority (CA). The digital certificate binds the identity information of a VPN gateway (e.g., hostname or IP address) to the device’s public key by means of digital signature. This involves the use of public key cryptography algorithms, such as RSA. Based on this binding, any device that trusts the CA certificate, i.e., trusts the signature of the CA, would accept the identity inside the signed certificate. This model enables all VPN gateways and clients that trust the same CA to authenticate each other. Information Assurance OfficerECSC-1
    SV-40986r1_rule NET-VPN-040 MEDIUM The VPN gateway must only accept certificates issued by a DoD-approved Certificate Authority when using PKI for authentication. When using digital certificates, Internet Key Exchange (IKE) negotiation between peers is restricted by either manually configuring each peer with the public key for each peer to which it is allowed to connect, or enrolling each peer with a Certificate Authority (CA). All peers to which the peer is allowed to connect must enroll with the same CA server and belong to the same organization. Certificates are issued and signed by a CA. Hence, the signature on a certificate identifies the particular CA that issued a certificate. The CA in turn has a certificate that binds its identity to its public key, so the CA’s identity can be verified. The primary role of the CA is to digitally sign and publish the public key bound to a given user or device via a digital certificate. This is done using the CA's own private key, so that trust in the user’s key relies on trust in the validity of the CA's key. Hence, to establish trust in the certificate of the remote client or peer, the VPN gateway must be configured to validate the peer’s certificate with the DoD-approved CA, as well as validate the identity of the DoD-approved CA. If the peer’s certificate is not validated, there is a risk of establishing an IPSec Security Association with a malicious user or a remote client that is not authorized. Information Assurance OfficerECSC-1
    SV-40987r1_rule NET-VPN-250 MEDIUM The VPN gateway server must enforce a policy to the software client to disallow the remote client from being able to save the logon password locally on the remote PC. Enabling the password save function requires users to only enter their password once when establishing the VPN tunnel. After that the software client will automatically re-enter the password when prompted for credentials by the VPN gateway.Information Assurance OfficerECSC-1
    SV-40988r1_rule NET-VPN-240 MEDIUM The VPN gateway server must enforce a policy to the software client to display a DoD approved warning banner prior to allowing access to the VPN. All software remote clients must present a DoD approved warning banner prior allowing access to VPN. 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 network is subject to monitoring to detect unauthorized usage. Failure to display the required warning banner prior to logon attempts will limit the 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. 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 OfficerECSC-1
    SV-40989r1_rule NET-VPN-050 MEDIUM The VPN gateway must not accept certificates that have been revoked when using PKI for authentication. Situations may arise in which the certificate issued by a Certificate Authority (CA) may need to be revoked before the lifetime of the certificate expires. For example, the certificate is known to have been compromised. To achieve this, a list of certificates that have been revoked, known as a Certificate Revocation List (CRL), is sent periodically from the CA to the IPSec gateway. When an incoming Internet Key Exchange (IKE) session is initiated for a remote client or peer whose certificate is revoked, the CRL will be checked to see if the certificate is valid; if the certificate is revoked, IKE will fail and an IPSec security association will not be established for the remote end-point.Information Assurance OfficerECSC-1
    SV-40990r1_rule NET-VPN-230 MEDIUM The VPN gateway server must enforce a policy to the remote software client to check for the presence of a personal firewall before enabling access to the VPN. The security posture of the remote PC connecting to the enclave via VPN is vital to the overall security of the enclave. While on-site hosts are behind the enclave’s perimeter defense, a remote PC is not and therefore is exposed to many vulnerabilities existing in the Internet when connected to a service provider via dial-up or broadband connection. Though it is policy to have a firewall installed on the remote PC according to the Secure Remote Computing Endpoint STIG (SRC-EPT-405), it is imperative the VPN gateway enforce the policy to the software client to verify the firewall is active prior to enabling access to the VPN.Information Assurance OfficerECSC-1
    SV-40992r1_rule NET-VPN-060 HIGH The VPN gateway must use Secure Hash Algorithm for IKE cryptographic hashing operations required for authentication and integrity verification. Because hash algorithms create a short fixed-length hash value to represent data of any size, there are far more possible input values than there are unique hash values. Hence, multiple input values exist that will produce the same hash value. This is known as a collision and for a hash function to be deemed cryptographically secure and collision resistant, it has to be hard to find two inputs that hash to the same output. Various methods have been published stating that an MD5 collision has been found in less than a minute. Therefore, MD5 is considered cryptographically broken and should be not be used—and certainly not for security-based services relying on collision resistance. Using a weak hash algorithm such as MD5 could enable a rogue device to discover the authentication key enabling it to establish an Internet Key Exchange (IKE) Security Association with either of the VPN end points. Hence, Secure Hash Algorithm (SHA) must be used for IKE cryptographic hashing operations required for authentication and integrity verification.Information Assurance OfficerECSC-1
    SV-40993r1_rule NET-VPN-220 MEDIUM The VPN gateway server must enforce a no split-tunneling policy to all remote clients. A VPN hardware or software client with split tunneling enabled provides an unsecured backdoor to the enclave from the Internet. With split tunneling enabled, a remote client has access to the Internet while at the same time has established a secured path to the enclave via an IPSec tunnel. A remote client connected to the Internet that has been compromised by an attacker in the Internet, provides an attack base to the enclave’s private network via the IPSec tunnel. Hence, it is imperative that the VPN gateway enforces a no split-tunneling policy to all remote clients.Information Assurance OfficerECSC-1
    SV-40994r1_rule NET-VPN-070 HIGH The VPN gateway must use AES for IKE cryptographic encryption operations required to ensure privacy of the IKE session. While there is much debate about the security and performance of Advance Encryption Standard (AES), there is a consensus that it is significantly more secure than any of the algorithms supported by IPSec implementations today. AES is available in three key sizes: 128, 192 and 256 bits, versus the 56 bit DES. Therefore, there are approximately 1021 times more AES 128-bit keys than DES 56-bit keys. In addition, AES uses a block size of 128 bits—twice the size of DES or 3DES. To ensure the privacy of the IKE session responsible for establishing the security association and key exchange for an IPSec tunnel, it is imperative that AES is used for encryption operations.Information Assurance OfficerECSC-1
    SV-40995r1_rule NET-VPN-210 MEDIUM The VPN gateway peer at a remote site must receive all ingress traffic and forward all egress traffic via the IPSec tunnel or other provisoned WAN links connected to the central or remote site. A VPN gateway peer at the remote site provides connectivity to the central or other remote sites belonging to the enclave via an IPSec tunnel across an IP backbone network such as the NIPRNet. This creates an extension or Intranet for the enclave using IPSec tunnels in lieu of traditional or legacy WAN services (T carrier, ATM, frame relay, etc). Unless the remote site has the required enclave perimeter defense (firewall, IPS, deny by default, etc), it is imperative that all inbound and outbound traffic traverse only the IPSec tunnels or other provisioned WAN links connecting the remote site to other sites belonging to the enclave. In other words, no packets can leak out an external-facing interface as “native” IP traffic into an IP backbone (i.e. NIPRNet, Internet). In addition, the external interface must not receive any traffic that is not secured by an IPSec tunnel or other provisioned WAN links connected to the central or remote site. This not only ensures that inbound and outbound traffic does not bypass the enclave’s perimeter defense, but also eliminates any backdoor connection. Information Assurance OfficerECSC-1
    SV-40996r1_rule NET-VPN-200 MEDIUM The VPN gateway must ensure traffic from a remote client with an outbound destination does not bypass the enclaves perimeter defense mechanisms deployed for egress traffic. Packets from a remote client destined outbound must be inspected and proxied the same as any other traffic that will egress the enclave. Otherwise, there is the risk that the return traffic that will ingress the IPSec tunnel could compromise the remote client and possibly the remote LAN. This scenario can exist with a VPN-on-a-stick implementation that allows traffic to u-turn—that is, traffic from the remote site that traverses the IPSec tunnel is immediately forwarded out the same interface towards the NIPRNet and Internet with no upstream firewall. If a remote LAN is breached, the entire enclave could be exposed via the secured tunnel or any other provisioned link between the compromised remote LAN and other remote sites and the central site. Hence, it is imperative that traffic from the remote site that is destined outbound does not bypass the applicable inspection and proxy services deployed for the enclave’s perimeter defense. Information Assurance OfficerECSC-1
    SV-40997r2_rule NET-VPN-190 HIGH IPSec Security Association parameters must be compliant with all requirements specified for VPN Suite B when transporting classified traffic across a non-classified network. RFC 6379 Suite B Cryptographic Suites for IPSec defines four cryptographic user interface suites for deploying IPSec. Each suite provides choices for Encapsulating Security Payload (ESP) and Internet Key Exchange (IKE). The four suites are differentiated by the choice of IKE authentication and key exchange, cryptographic algorithm strengths, and whether ESP is to provide both confidentiality and integrity or integrity only. The suite names are based on the Advanced Encryption Standard (AES) mode and AES key length specified for ESP. Two suites are defined for transporting classified information up to SECRET level—one for both confidentiality and integrity and one for integrity only. There are also two suites defined for transporting classified information up to TOP SECRET level.Information Assurance OfficerECSC-1
    SV-40998r1_rule NET-VPN-180 MEDIUM The VPN gateway must enable anti-replay for all IPSec security associations. Replay attack is a type of injection attack when an IPSec packet is captured by an attacker and re-inserts it into the legitimate flow to disrupt service or create undesired behavior. IPSec anti-replay service can mitigate a replay attack by running sequence numbers for each end of the tunnel and incrementing it for each packet sent. If a packet that is received does not have the expected sequence number, it is dropped. Information Assurance OfficerECSC-1
    SV-40999r1_rule NET-VPN-080 LOW The VPN gateway must use IKE main mode for the purpose of negotiating an IPSec security association policy when pre-shared keys are used for authentication Aggressive mode is completed using only three messages instead of the six used in main mode. Essentially, all the information needed to generate the Diffie-Hellman secret is exchanged in the first two messages exchanged between the two peers. The identity of the peer is also exchanged in the first two packets which have been sent in the clear. There are risks to configurations that use pre-shared keys which are exaggerated when aggressive mode is used. The entire session may be intercepted and manipulated. An adversary can either use a pre-shared key to impersonate a trusted end-point or client and connect to the protected network, or it can mount a Man-in-the-Middle attack on any new session.Information Assurance OfficerECSC-1
    SV-41001r2_rule NET-VPN-090 LOW The VPN gateway must use a key size from Diffie-Hellman Group 14 or larger during IKE Phase 1. Diffie-Hellman (DH) is a public-key cryptography scheme that allows two parties to establish a shared secret over an insecure communications channel. IKE uses DH to create keys used to encrypt both the Internet Key Exchange (IKE) and IPsec communication channels. The process works by two peers both generating a private and a public key and then exchanging their public keys with each other. The peers produce the same shared secret by using each other’s public key and their own private key using the DH algorithm. The DH group is configured as part of the IKE Phase 1 key exchange settings. DH public key cryptography is used by all major VPN gateways. DH group 1 consists of a 768 bit modulus, group 2 consists of 1024 bit modulus, group 5 uses a 1536 bit modulus, and group 14 uses a 2048 bit modulus. The security of the DH key exchange is based on the difficulty of solving the discrete logarithm in which the key was derived from. Hence, the larger the modulus, the more secure the generated key is considered to be.
    SV-41002r1_rule NET-VPN-100 MEDIUM The VPN gateway must specify Perfect Forward Secrecy during IKE negotiation. The Internet Key Exchange (IKE) Phase-2 (Quick Mode) Security Association (SA) is used to create an IPSec session key. Hence, its rekey or key regeneration procedure is very important. The Phase-2 rekey can be performed with or without Perfect Forward Secrecy (PFS). With PFS, every time a new IPSec Security Association is negotiated during the Quick Mode, a new Diffie-Hellman (DH) exchange occurs. The new DH shared secret will be included with original keying material (SYKEID_d, initiator nonce, and responder nonce from Phase 1) for generating a new IPSec session key. If PFS is not used, the IPSec session key will always be completely dependent on the original keying material from the Phase-1. Hence, if an older key is compromised at any time, it is possible that all new keys may be compromised. The DH exchange is performed in the same manner as was done in Phase 1 (Main or Aggressive Mode). However, the Phase-2 exchange is protected by encrypting the Phase-2 packets with the key derived from the Phase-1 negotiation. Because DH negotiations during Phase-2 are encrypted, the new IPSec session key has an added element of secrecy. Information Assurance OfficerECSC-1
    SV-41003r1_rule NET-VPN-170 LOW The VPN gateway must implement IPSec security associations that terminate after one hour or less of idle time. When a VPN gateway creates an IPSec Security Association (SA), resources must be allocated to maintain the SA. These resources are wasted during periods of IPSec endpoint inactivity which could result in the gateway’s inability to create new SAs for other endpoints; thereby, preventing new sessions from connecting. The IPSec SA idle timer allows SAs associated with inactive endpoints to be deleted before the SA lifetime has expired.Information Assurance OfficerECSC-1
    SV-41004r1_rule NET-VPN-160 LOW The VPN gateway must implement IPSec security associations that terminate within 8 hours or less. The IPSec SA and its corresponding key will expire either after the number of seconds or amount of traffic volume has exceeded the configured limit. A new SA is negotiated before the lifetime threshold of the existing SA is reached to ensure that a new SA is ready for use when the old one expires. The longer the life time of the IPSec Security Association, the longer the life time of the session key used to protect IP traffic. The SA is less secure with a longer lifetime because an attacker has a greater opportunity to collect traffic encrypted by the same key and subject it to cryptanalysis. However, a shorter lifetime causes IPSec peers to have to renegotiate IKE Phase II more often resulting in the expenditure of additional resources. Nevertheless, it is imperative the IPSec SA lifetime terminates within 8 hours.Information Assurance OfficerECSC-1
    SV-41005r2_rule NET-VPN-110 LOW The VPN gateway must use a key size from Diffie-Hellman Group 14 or larger during IKE Phase 2. Diffie-Hellman (DH) is a public -key cryptography scheme allowing two parties to establish a shared secret over an insecure communications channel. IKE uses Diffie-Hellman to create keys used to encrypt both the Internet Key Exchange (IKE) and IPsec communication channels. The process works by two peers both generating a private and a public key and then exchanging their public keys with each other. The peers produce the same shared secret by using each other’s public key and their own private key using the DH algorithm. With Perfect Forward Secrecy (PFS), every time a new IPsec SA is negotiated during the Quick Mode, a new DH exchange occurs. The new DH shared secret will be included with original keying material (SYKEID_d, initiator nonce, and responder nonce from Phase 1) for generating a new IPsec session key. If PFS is not used, the IPsec session key will always be completely dependent on the original keying material from the Phase-1. Hence, if an older key is compromised at any time, it is possible that all new keys may be compromised.
    SV-41006r1_rule NET-VPN-150 HIGH The VPN gateway must use ESP tunnel mode for establishing secured paths to transport traffic between the organization’s sites or between a gateway and remote end-stations. Encapsulating Security Payload (ESP) is the feature in the IPSec architecture providing confidentiality, data origin authentication, integrity, and anti-replay services. ESP can be deployed in either transport or tunnel mode. Transport mode is used to create a secured session between two hosts. It can also be used when two hosts simply want to authenticate each IP packet with IPSec authentication header (AH). With ESP transport mode, only the payload (transport layer) is encrypted; whereas with tunnel mode, the entire IP packet is encrypted and encapsulated with a new IP header. Tunnel mode is used to encrypt traffic between secure IPSec gateways, or between an IPSec gateway and an end-station running IPSec software. Hence, it is the only method to provide secured path to transport traffic between remote sites or end-stations and the central site.Information Assurance OfficerECSC-1
    SV-41007r1_rule NET-VPN-120 LOW The VPN gateway must implement IKE Security Associations that terminate within 24 hours or less. The Security Association (SA) and its corresponding key will expire after the number of seconds has exceeded the configured limit. A new SA is negotiated before the lifetime threshold of the existing SA is reached to ensure a new SA is ready for use when the old one expires. The longer the life time of the Internet Key Exchange (IKE) Security Association, the longer the life time of the key used for the IKE session, which is the control plane for establishing IPSec Security Associations. The SA is less secure with a longer lifetime because an attacker has a greater opportunity to collect traffic encrypted by the same key and subject it to cryptanalysis. However, a shorter IKE lifetime causes IPSec peers to have to renegotiate IKE more often resulting in the expenditure of additional resources. Nevertheless, it is imperative the IKE SA lifetime terminates within 24 hours or less.Information Assurance OfficerECSC-1
    SV-41008r1_rule NET-VPN-140 HIGH The VPN gateway must use AES for IPSec cryptographic encryption operations required to ensure privacy of the IPSec session. While there is much debate about the security and performance of Advance Encryption Standard (AES), there is a consensus it is significantly more secure than any of the algorithms supported by IPSec implementations today. AES is available in three key sizes: 128, 192 and 256 bits, versus the 56 bit DES. Therefore, there are approximately 1021 times more AES 128-bit keys than DES 56-bit keys. In addition, AES uses a block size of 128 bits—twice the size of DES or 3DES. Hence, AES must be used to ensure the privacy of the IPSec tunnel. Information Assurance OfficerECSC-1
    SV-41009r1_rule NET-VPN-130 HIGH The VPN gateway must use Secure Hash Algorithm for IPSec cryptographic hashing operations required for authentication and integrity verification. Because hash algorithms create a short fixed-length hash value to represent data of any size, there are far more possible input values than there are unique hash values. Hence, multiple input values exist that will produce the same hash value. This is known as a collision. For a hash function to be deemed cryptographically secure and collision resistant, it has to be hard to find two inputs that hash to the same output. Various methods have been published stating that an MD5 collision has been found in less than a minute. Therefore MD5 is considered cryptographically broken and should not be used—and certainly not for security-based services relying on collision resistance. Hence Secure Hash Algorithm (SHA) must be used for IPSec cryptographic hashing operations required for authentication and integrity verification.Information Assurance OfficerECSC-1
    SV-41553r3_rule NET0408 MEDIUM Network devices must authenticate all BGP peers within the same or between autonomous systems (AS). As specified in RFC 793, TCP utilizes sequence checking to ensure proper ordering of received packets. RFC 793 also specifies that RST (reset) control flags should be processed immediately, without waiting for out of sequence packets to arrive. RFC 793 also requires that sequence numbers are checked against the window size before accepting data or control flags as valid. A router receiving an RST segment will close the TCP session with the BGP peer that is being spoofed; thereby, purging all routes learned from that BGP neighbor. A RST segment is valid as long as the sequence number is within the window. The TCP reset attack is made possible due to the requirements that Reset flags should be processed immediately and that a TCP endpoint must accept out of order packets that are within the range of a window size. This reduces the number of sequence number guesses the attack must make by a factor equivalent to the active window size. Each sequence number guess made by the attacker can be simply incremented by the receiving connections window size. The BGP peering session can protect itself against such an attack by authenticating each TCP segment. The TCP header options include an MD5 signature in every packet and are checked prior to the acceptance and processing of any TCP packet--including RST flags. One way to create havoc in a network is to advertise bogus routes to a network. A rogue router could send a fictitious routing update to convince a BGP router to send traffic to an incorrect or rogue destination. This diverted traffic could be analyzed to learn confidential information of the site's network, or merely used to disrupt the network's ability to effectively communicate with other networks. An autonomous system can advertise incorrect information by sending BGP updates messages to routers in a neighboring AS. A malicious AS can advertise a prefix originated from another AS and claim that it is the originator (prefix hijacking). Neighboring autonomous systems receiving this announcement will believe that the malicious AS is the prefix owner and route packets to it.ECSC-1