| name | SC-7(5)_deny-by-default-allow-by-exception |
| description | Deny network communications traffic by default and allow network communications traffic by exception [organization-defined]. |
| category | configuration |
| version | 5.2.0 |
| author | cyberstrike-official |
| tags | ["nist","sp800-53","rev5","sc-7-5","sc","enhancement"] |
| tech_stack | ["aws","azure","gcp","linux","windows","network"] |
| cwe_ids | ["CWE-311"] |
| chains_with | [] |
| prerequisites | ["SC-7"] |
| severity_boost | {} |
SC-7(5) Deny by Default — Allow by Exception
Enhancement of: SC-7
High-Level Description
Family: System and Communications Protection (SC)
Framework: NIST SP 800-53 Rev 5
Denying by default and allowing by exception applies to inbound and outbound network communications traffic. A deny-all, permit-by-exception network communications traffic policy ensures that only those system connections that are essential and approved are allowed. Deny by default, allow by exception also applies to a system that is connected to an external system.
What to Check
How to Test
Step 1: Review Documentation
Examine the System Security Plan (SSP) and related artifacts for SC-7(5) implementation details. Verify the organization has documented how this control is satisfied.
Step 2: Validate Implementation
# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly
# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null
Step 3: Test Operating Effectiveness
Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.
Tools
| Tool | Purpose | Usage |
|---|
| cloud-audit-mcp | Check encryption and network controls | cloud_audit_encryption |
| nmap | Network scanning | nmap -sV --script ssl-enum-ciphers |
Remediation Guide
Control Statement
Deny network communications traffic by default and allow network communications traffic by exception [organization-defined].
Implementation Guidance
Denying by default and allowing by exception applies to inbound and outbound network communications traffic. A deny-all, permit-by-exception network communications traffic policy ensures that only those system connections that are essential and approved are allowed. Deny by default, allow by exception also applies to a system that is connected to an external system.
