Virtual Private Network (VPN) Security Requirements Guide
Rules, Groups, and Values defined within the XCCDF Benchmark
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The VPN Gateway must be configured to prohibit the use of all unnecessary and/or nonsecure functions, ports, protocols, and/or services, as defined in the PPSM CAL and vulnerability assessments.
In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types); organizations must disable...Rule Medium Severity -
The Remote Access VPN Gateway must be configured to prohibit Point-to-Point Tunneling Protocol (PPTP) and L2F.
The PPTP and L2F are obsolete method for implementing virtual private networks. Both protocols may be easy to use and readily available, but they have many well-known security issues and exploits. ...Rule Medium Severity -
The VPN Client must implement multifactor authentication for network access to nonprivileged accounts such that one of the factors is provided by a device separate from the system gaining access.
Using an authentication device, such as a common access card (CAC) or token that is separate from the information system, ensures that even if the information system is compromised, that compromise...Rule Medium Severity -
The TLS VPN must be configured to use replay-resistant authentication mechanisms for network access to nonprivileged accounts.
A replay attack may enable an unauthorized user to gain access to the application. Authentication sessions between the authenticator and the application validating the user credentials must not be ...Rule Medium Severity -
The VPN Gateway must uniquely identify all network-connected endpoint devices before establishing a connection.
Without identifying devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity. For distributed architectures (e.g., service-oriented architectures), the d...Rule Medium Severity -
The Remote Access VPN Gateway must use a separate authentication server (e.g., LDAP, RADIUS, TACACS+) to perform user authentication.
The VPN interacts directly with public networks and devices and should not contain user authentication information for all users. AAA network security services provide the primary framework through...Rule Medium Severity -
The VPN Gateway must invalidate session identifiers upon user logoff or other session termination.
Captured sessions can be reused in "replay" attacks. This requirement limits the ability of adversaries from capturing and continuing to employ previously valid session IDs. Session IDs are tokens...Rule Medium Severity -
The VPN Gateway must recognize only system-generated session identifiers.
VPN gateways (depending on function) utilize sessions and session identifiers to control application behavior and user access. If an attacker can guess the session identifier, or can inject or manu...Rule Medium Severity -
The VPN Gateway must be configured to perform an organization-defined action if the audit reveals unauthorized activity.
Remote access devices, such as those providing remote access to network devices and information systems, which lack automated control capabilities, increase risk and makes remote user access manage...Rule Medium Severity -
The VPN Gateway administrator accounts or security policy must be configured to allow the system administrator to immediately disconnect or disable remote access to devices and/or users when needed.
Without the ability to immediately disconnect or disable remote access, an attack or other compromise taking progress would not be immediately stopped. Remote access functionality must have the ca...Rule Medium Severity -
The VPN Gateway must generate a log record or an SNMP trap that can be forwarded as an alert to, at a minimum, the SCA and ISSO, of all log failure events where the detection and/or prevention function is unable to write events to either local storage or the centralized server.
It is critical for the appropriate personnel to be aware if a system is at risk of failing to process audit logs as required. Without a real-time alert, security personnel may be unaware of an impe...Rule Medium Severity -
The VPN Gateway must disable split-tunneling for remote clients VPNs.
Split tunneling would in effect allow unauthorized external connections, making the system more vulnerable to attack and to exfiltration of organizational information. A VPN hardware or software c...Rule Medium Severity -
The VPN Gateway and Client must be configured to protect the confidentiality and integrity of transmitted information.
Without protection of the transmitted information, confidentiality and integrity may be compromised as unprotected communications can be intercepted and either read or altered. This requirement al...Rule High Severity -
The VPN Gateway must generate log records when successful and/or unsuccessful VPN connection attempts occur.
Without generating log records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an inci...Rule Medium Severity -
The VPN Gateway must use a FIPS-validated cryptographic module to implement encryption services for unclassified information requiring confidentiality.
FIPS 140-2 precludes the use of invalidated cryptography for the cryptographic protection of sensitive or valuable data within Federal systems. Unvalidated cryptography is viewed by NIST as providi...Rule Medium Severity -
The IPsec VPN Gateway must use Internet Key Exchange (IKE) for IPsec VPN Security Associations (SAs).
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 ...Rule High Severity -
For site-to-site, VPN Gateway must be configured to store only cryptographic representations of pre-shared Keys (PSKs).
PSKs need to be protected at all times, and encryption is the standard method for protecting passwords. If PSKs are not encrypted, they can be plainly read and easily compromised. Use of passwords ...Rule Medium Severity -
The IPsec VPN must use AES256 or greater encryption for the IPsec proposal to protect the confidentiality of remote access sessions.
Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DOD nonpublic information s...Rule High Severity -
The VPN remote access server must be configured use cryptographic algorithms approved by NSA to protect NSS for remote access to a classified network.
Use of weak or untested encryption algorithms undermines the purposes of utilizing encryption to protect data. The VPN gateway must implement cryptographic modules adhering to the higher standards ...Rule High Severity -
The VPN Gateway must validate certificates used for Transport Layer Security (TLS) functions by performing RFC 5280-compliant certification path validation.
A certificate's certification path is the path from the end entity certificate to a trusted root certification authority (CA). Certification path validation is necessary for a relying party to make...Rule Medium Severity
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