NIST 800-53 REV 5 • SYSTEM AND COMMUNICATIONS PROTECTION
SC-7(23) — Disable Sender Feedback on Protocol Validation Failure
Disable feedback to senders on protocol format validation failure.
CMMC Practice Mapping
No direct CMMC mapping
NIST 800-171 Mapping
No direct NIST 800-171 mapping
Related Controls
No related controls listed
Supplemental Guidance
Disabling feedback to senders when there is a failure in protocol validation format prevents adversaries from obtaining information that would otherwise be unavailable.
Practitioner Notes
When your boundary devices detect malformed or invalid protocol data, they should not send detailed error messages back to the sender. Detailed errors help attackers refine their techniques.
Example 1: Configure your WAF to return generic "403 Forbidden" or "400 Bad Request" responses when it blocks malicious input. Never include details about which specific rule triggered the block or what the WAF expected to see.
Example 2: On your mail gateway, configure it to silently drop or quarantine emails that fail protocol validation rather than sending bounce messages that reveal your mail server software, version, or internal hostnames.