# SI-4(21)_probationary-periods

> Implement the following additional monitoring of individuals during [organization-defined]: [organization-defined].

- Skill: `cyberstrikeus/si-4-21-probationary-periods` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/si-4-21-probationary-periods`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/si-4-21-probationary-periods/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/si-4-21-probationary-periods

---


# SI-4(21) Probationary Periods

> **Enhancement of:** SI-4

## High-Level Description

**Family:** System and Information Integrity (SI)
**Framework:** NIST SP 800-53 Rev 5

During probationary periods, employees do not have permanent employment status within organizations. Without such status or access to information that is resident on the system, additional monitoring can help identify any potentially malicious activity or inappropriate behavior.

## What to Check

- [ ] Verify SI-4(21) Probationary Periods is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for SI-4(21)
- [ ] Verify enhancement builds upon base control SI-4

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SI-4(21) 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 integrity monitoring | `cloud_audit_monitoring`       |
| AWS CLI         | Review GuardDuty/Inspector | `aws guardduty list-detectors` |

## Remediation Guide

### Control Statement

Implement the following additional monitoring of individuals during [organization-defined]: [organization-defined].

### Implementation Guidance

During probationary periods, employees do not have permanent employment status within organizations. Without such status or access to information that is resident on the system, additional monitoring can help identify any potentially malicious activity or inappropriate behavior.

## Risk Assessment

| Finding                                       | Severity | Impact                                      |
| --------------------------------------------- | -------- | ------------------------------------------- |
| SI-4(21) Probationary Periods not implemented | High     | System and Information Integrity            |
| SI-4(21) partially implemented                | Medium   | Incomplete System and Information Integrity |

## CWE Categories

| CWE ID | Title                     |
| ------ | ------------------------- |
| CWE-20 | Improper Input Validation |

## References

- [NIST SP 800-53 Rev 5 - SI-4(21)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=si-4.21)
- [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 (AC-18) reviewed