# AC-9(4)_additional-logon-information

> Notify the user, upon successful logon, of the following additional information: [organization-defined].

- Skill: `cyberstrikeus/ac-9-4-additional-logon-information` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/ac-9-4-additional-logon-information`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/ac-9-4-additional-logon-information/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-9-4-additional-logon-information

---


# AC-9(4) Additional Logon Information

> **Enhancement of:** AC-9

## High-Level Description

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

Organizations can specify additional information to be provided to users upon logon, including the location of the last logon. User location is defined as information that can be determined by systems, such as Internet Protocol (IP) addresses from which network logons occurred, notifications of local logons, or device identifiers.

## What to Check

- [ ] Verify AC-9(4) Additional Logon Information is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for AC-9(4)
- [ ] 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(4) 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 following additional information: [organization-defined].

### Implementation Guidance

Organizations can specify additional information to be provided to users upon logon, including the location of the last logon. User location is defined as information that can be determined by systems, such as Internet Protocol (IP) addresses from which network logons occurred, notifications of local logons, or device identifiers.

## Risk Assessment

| Finding                                              | Severity | Impact                    |
| ---------------------------------------------------- | -------- | ------------------------- |
| AC-9(4) Additional Logon Information not implemented | High     | Access Control            |
| AC-9(4) 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(4)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ac-9.4)
- [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