# AC-9(1)_unsuccessful-logons

> Notify the user, upon successful logon, of the number of unsuccessful logon attempts since the last successful logon.

- Skill: `cyberstrikeus/ac-9-1-unsuccessful-logons` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/ac-9-1-unsuccessful-logons`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/ac-9-1-unsuccessful-logons/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/ac-9-1-unsuccessful-logons

---


# AC-9(1) Unsuccessful Logons

> **Enhancement of:** AC-9

## High-Level Description

**Family:** Access Control (AC)
**Framework:** NIST SP 800-53 Rev 5

Information about the number of unsuccessful logon attempts since the last successful logon allows the user to recognize if the number of unsuccessful logon attempts is consistent with the user’s actual logon attempts.

## What to Check

- [ ] Verify AC-9(1) Unsuccessful Logons is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for AC-9(1)
- [ ] Verify enhancement builds upon base control AC-9

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AC-9(1) 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 IAM policies and access controls | `cloud_audit_iam_policies` |
| hackbrowser | Test web application access controls   | `hackbrowser`        |

## Remediation Guide

### Control Statement

Notify the user, upon successful logon, of the number of unsuccessful logon attempts since the last successful logon.

### Implementation Guidance

Information about the number of unsuccessful logon attempts since the last successful logon allows the user to recognize if the number of unsuccessful logon attempts is consistent with the user’s actual logon attempts.

## Risk Assessment

| Finding                                     | Severity | Impact                    |
| ------------------------------------------- | -------- | ------------------------- |
| AC-9(1) Unsuccessful Logons not implemented | High     | Access Control            |
| AC-9(1) partially implemented               | Medium   | Incomplete Access Control |

## CWE Categories

| CWE ID  | Title                   |
| ------- | ----------------------- |
| CWE-284 | Improper Access Control |

## References

- [NIST SP 800-53 Rev 5 - AC-9(1)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ac-9.1)
- [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 (none) reviewed