NIST Special Publication 800-171 Revision 2

Date Published: January 28th, 2021

Withdrawn on May 14, 2024. Superseded by SP 800-171 Rev. 3

Author(s): Ron Ross (NIST), Victoria Pillitteri (NIST), Kelley Dempsey (NIST), Mark Riddle (NARA), Gary Guissanie (IDA)

Note: A Class Deviation is in effect as of May 2, 2024 (DEVIATION 2024O0013). The deviation clause requires contractors, who are subject to 252.204-7012, to comply with National Institute of Standards and Technology (NIST) Special Publication (SP) 800-171 Revision 2, instead of the version of NIST SP 800-171 in effect at the time the solicitation is issued or as authorized by the contracting officer. Click Here

3.1.13 Employ cryptographic mechanisms to protect the confidentiality of remote access sessions.

Control Family: Access Control

Control Type: Derived

SPRS Value: 5

SPRS Supplemental Guidance:

Do not subtract points if remote access not permitted

CMMC Level(s): AC.L2-3.1.13

Top Ten Failed Requirement: No

Referenced in:

DFARS 252.204-7012

Derived From: NIST SP 800-53r4

AC-17(2)

NIST Supplemental Guidance:

  • NIST SP 800-46

  • NIST SP 800-77

  • NIST SP 800-113

Discussion:

Cryptographic standards include FIPS-validated cryptography and NSA-approved cryptography. See [NIST CRYPTO]; [NIST CAVP]; [NIST CMVP]; National Security Agency Cryptographic Standards.

Determining Statements (NIST SP 800-171Ar2)

Upon assessment, assessors must determine if-

3.1.13[a] cryptographic mechanisms to protect the confidentiality of remote access
sessions are identified.
3.1.13[b] cryptographic mechanisms to protect the confidentiality of remote access
sessions are implemented.

Assessors are instructed to-

Examine: [SELECT FROM: Access control policy; procedures addressing remote access to the system; system security plan; system design documentation; system configuration settings and associated documentation; cryptographic mechanisms and associated configuration documentation; system audit logs and records; other relevant documents or records].

Interview: [SELECT FROM: System or network administrators; personnel with information security responsibilities; system developers].

Test: [SELECT FROM: Cryptographic mechanisms protecting remote access sessions]

FURTHER DISCUSSION

A remote access session involves logging into the organization’s systems such as its internal network or a cloud service provider from a remote location such as home or an alternate work site. Because the use of cryptography in this requirement is to protect the confidentiality of CUI, the cryptography used must meet the criteria specified in requirement SC.L2-3.13.11. Although not explicitly required to meet AC.L2-3.1.13 requirements, this remote access session must be secured using FIPS-validated cryptography to provide confidentiality and prevent anyone from deciphering session information exchanges.

This requirement, AC.L2-3.1.13, requires the use of cryptographic mechanisms when enabling remote sessions and complements five other requirements dealing with remote access (AC.L2-3.1.12, AC.L2-3.1.14, AC.L2-3.1.15, IA.L2-3.5.3, and MA.L2-3.7.5):

  • AC.L2-3.1.12 requires the control of remote access sessions.

  • AC.L2-3.1.14 limits remote access to specific access control points.

  • AC.L2-3.1.15 requires authorization for privileged commands executed during a remote session.

  • IA.L2-3.5.3 requires multifactor authentication for network access to non-privileged accounts.

  • Finally, MA.L2-3.7.5 requires the addition of multifactor authentication for remote maintenance sessions.

Example

You are responsible for implementing a remote network access capability for users who access CUI remotely. In order to provide session confidentiality, you decide to implement a VPN mechanism and select a product that has completed FIPS 140 validation [a,b].

Potential Assessment Considerations

  • Are cryptographic mechanisms used for remote access sessions (e.g., Transport Layer Security (TLS) and Internet Protocol Security (IPSec) using FIPS-validated encryption algorithms) defined and implemented [a,b]? Note that simply using an approved algorithm is not sufficient – the module (software and/or hardware) used to implement the algorithm must be separately validated under FIPS 140.

Frameworks & Controls