# SC-7(18)_fail-secure

> Prevent systems from entering unsecure states in the event of an operational failure of a boundary protection device.

- Skill: `cyberstrikeus/sc-7-18-fail-secure` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/sc-7-18-fail-secure`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/sc-7-18-fail-secure/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/sc-7-18-fail-secure

---


# SC-7(18) Fail Secure

> **Enhancement of:** SC-7

## High-Level Description

**Family:** System and Communications Protection (SC)
**Framework:** NIST SP 800-53 Rev 5

Fail secure is a condition achieved by employing mechanisms to ensure that in the event of operational failures of boundary protection devices at managed interfaces, systems do not enter into unsecure states where intended security properties no longer hold. Managed interfaces include routers, firewalls, and application gateways that reside on protected subnetworks (commonly referred to as demilitarized zones). Failures of boundary protection devices cannot lead to or cause information external to the devices to enter the devices nor can failures permit unauthorized information releases.

## What to Check

- [ ] Verify SC-7(18) Fail Secure is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for SC-7(18)
- [ ] Verify enhancement builds upon base control SC-7

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SC-7(18) 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

Prevent systems from entering unsecure states in the event of an operational failure of a boundary protection device.

### Implementation Guidance

Fail secure is a condition achieved by employing mechanisms to ensure that in the event of operational failures of boundary protection devices at managed interfaces, systems do not enter into unsecure states where intended security properties no longer hold. Managed interfaces include routers, firewalls, and application gateways that reside on protected subnetworks (commonly referred to as demilitarized zones). Failures of boundary protection devices cannot lead to or cause information external to the devices to enter the devices nor can failures permit unauthorized information releases.

## Risk Assessment

| Finding                              | Severity | Impact                                          |
| ------------------------------------ | -------- | ----------------------------------------------- |
| SC-7(18) Fail Secure not implemented | High     | System and Communications Protection            |
| SC-7(18) partially implemented       | Medium   | Incomplete System and Communications Protection |

## CWE Categories

| CWE ID  | Title                                |
| ------- | ------------------------------------ |
| CWE-311 | Missing Encryption of Sensitive Data |

## References

- [NIST SP 800-53 Rev 5 - SC-7(18)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=sc-7.18)
- [NIST SP 800-53A Rev 5 (Assessment Procedures)](https://csrc.nist.gov/pubs/sp/800/53/a/r5/final)
- [NIST SP 800-53 Rev 5 Full Catalog](https://csrc.nist.gov/pubs/sp/800/53/r5/upd1/final)

## Checklist

- [ ] Control documented in SSP
- [ ] Implementation evidence collected
- [ ] Operating effectiveness validated
- [ ] Continuous monitoring in place
- [ ] Related controls (CP-2, CP-12, SC-24) reviewed