Communications Authenticity
Protect the authenticity of communications sessions.
What gets scored, the objectives
SC.L2-3.13.15 is met only when every one of these 1 objectives, from NIST SP 800-171A, is satisfied. A single missed objective makes the whole requirement not met.
- a.the authenticity of communications sessions is protected
How this is assessed
NIST SP 800-171A defines three assessment methods. For SC.L2-3.13.15, whoever assesses it, including your own team in a self assessment, uses these:
System and communications protection policy; procedures addressing session authenticity; system security plan; system design documentation; system configuration settings and associated documentation; system audit logs and records; other relevant documents or records
System or network administrators; personnel with information security responsibilities
Mechanisms supporting or implementing session authenticity
What it means, in context
Authenticity protection includes protecting against man-in-the-middle attacks, session hijacking, and the insertion of false information into communications sessions . This requirement addresses communications protection at the session versus packet level (e.g., sessions in service-oriented architectures providing web-based services) and establishes grounds for confidence at both ends of communications sessions in ongoing identities of other parties and in the validity of information transmitted. NIST SP 800-77, NIST SP 800-95, and NIST SP 800-113 provide guidance on secure communications sessions.
The intent of this requirement is to ensure a trust relationship is established between both ends of a communication session. Each end can be assured that the other end is who it is supposed to be. This is often implemented using a mutual authentication handshake when the session is established, especially between devices. Session authenticity is usually provided by a security protocol enforced for a communication session. Choosing and enforcing a protocol will provide authenticity throughout a communications session. Example You are a system administrator responsible for ensuring that the two-factor user authentication mechanism for the servers is configured correctly . You purchase and maintain the digital certificate and replace it with a new one before the old one expires. You ensure the TLS configuration settings on the web servers, VPN solution, and other components that use TLS are correct, using secure settings that address risks against attacks on the encrypted sessions [a].
What passing evidence looks like
Session authenticity protected: modern protocols that bind sessions (TLS everywhere, Kerberos or token based auth), with legacy fallbacks disabled.
Common ways contractors fail SC.L2-3.13.15
- !Five points but largely earned by the legacy protocol cleanup you already did: legacy auth blocked, SMBv1 gone, TLS on services. Present those together as the session authenticity answer.
The step by step walkthrough for Microsoft 365 GCC High, Google Workspace, and on premises setups, plus the exact evidence to capture, lives inside the CMMC Level 2 plan.
Prove SC.L2-3.13.15, and the other 109
The Level 2 workspace walks your team through all 110 requirements at the objective level, drafts your SSP section by section from your own record for your team to read and accept, gives a prime or your own internal auditor a read only seat on the same record, and a credentialed officer reviews every step.
Book a free advisory callNo credit card, and Level 1 and Level 2 are both open, so sign up for the level your contracts call for. Self assessed and self attested: you score yourself in SPRS on a three year cycle and your senior official affirms it every year. As of September 3, 2026 a class deviation directs contracting officers to remove third party assessment from contracts. The program rule still provides for it, so your solicitation sets the track. Your team builds the same evidence either way. DFARS 252.204-7012 is unaffected, and the NIST SP 800-171 Rev 2 baseline is unchanged.
SC.L2-3.13.15 questions, answered
How many points is CMMC requirement SC.L2-3.13.15 worth?+
SC.L2-3.13.15 is worth 5 points in the CMMC Level 2 score under 32 CFR 170.24. If it is not met, you lose 5 from your total of 110.
Can SC.L2-3.13.15 be placed on a POA&M?+
No. SC.L2-3.13.15 must be fully met before you can file. It cannot be deferred to a POA&M, so it is a gate on your assessment.
What family does SC.L2-3.13.15 belong to?+
SC.L2-3.13.15 is in the System & Communications Protection (SC) family, one of the 14 families of NIST SP 800-171 that make up CMMC Level 2.
- NIST SP 800-171 Rev. 2 3.13.15