# IA-4(1)_prohibit-account-identifiers-as-public-identifiers

> Prohibit the use of system account identifiers that are the same as public identifiers for individual accounts.

- Skill: `cyberstrikeus/ia-4-1-prohibit-account-identifiers-as-public-identifiers` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/ia-4-1-prohibit-account-identifiers-as-public-identifiers`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/ia-4-1-prohibit-account-identifiers-as-public-identifiers/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/ia-4-1-prohibit-account-identifiers-as-public-identifiers

---


# IA-4(1) Prohibit Account Identifiers as Public Identifiers

> **Enhancement of:** IA-4

## High-Level Description

**Family:** Identification and Authentication (IA)
**Framework:** NIST SP 800-53 Rev 5

Prohibiting account identifiers as public identifiers applies to any publicly disclosed account identifier used for communication such as, electronic mail and instant messaging. Prohibiting the use of systems account identifiers that are the same as some public identifier, such as the individual identifier section of an electronic mail address, makes it more difficult for adversaries to guess user identifiers. Prohibiting account identifiers as public identifiers without the implementation of other supporting controls only complicates guessing of identifiers. Additional protections are required for authenticators and credentials to protect the account.

## What to Check

- [ ] Verify IA-4(1) Prohibit Account Identifiers as Public Identifiers is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for IA-4(1)
- [ ] Verify enhancement builds upon base control IA-4

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for IA-4(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 authentication settings  | `cloud_audit_iam_policies` |
| hackbrowser | Test authentication mechanisms | `hackbrowser`        |

## Remediation Guide

### Control Statement

Prohibit the use of system account identifiers that are the same as public identifiers for individual accounts.

### Implementation Guidance

Prohibiting account identifiers as public identifiers applies to any publicly disclosed account identifier used for communication such as, electronic mail and instant messaging. Prohibiting the use of systems account identifiers that are the same as some public identifier, such as the individual identifier section of an electronic mail address, makes it more difficult for adversaries to guess user identifiers. Prohibiting account identifiers as public identifiers without the implementation of other supporting controls only complicates guessing of identifiers. Additional protections are required for authenticators and credentials to protect the account.

## Risk Assessment

| Finding                                                                    | Severity | Impact                                       |
| -------------------------------------------------------------------------- | -------- | -------------------------------------------- |
| IA-4(1) Prohibit Account Identifiers as Public Identifiers not implemented | High     | Identification and Authentication            |
| IA-4(1) partially implemented                                              | Medium   | Incomplete Identification and Authentication |

## CWE Categories

| CWE ID  | Title                   |
| ------- | ----------------------- |
| CWE-287 | Improper Authentication |

## References

- [NIST SP 800-53 Rev 5 - IA-4(1)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ia-4.1)
- [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 (AT-2, PT-7) reviewed