# NIST SP 800-53 Rev. 5 AT-2(4) — Suspicious Communications And Anomalous System Behavior - Source: https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/at-2-4-suspicious-communications-and-anomalous-system-behavior - Section: [Compliance](https://support.icompaas.com/compliance) › [NIST SP 800-53 Rev. 5 Controls](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5) › AT — Awareness and Training - Last updated: 2026-06-05 - Publisher: iCompaas, Inc. (https://www.icompaas.com) **NIST SP 800-53 Rev. 5**·Control `AT-2(4)`·medium·Component: **Awareness and Training** ## What this control requires > Provides literacy training to recognize suspicious communications and anomalous system behavior, using defined indicators of malicious code, to enhance early detection and response. This control supports the Security Awareness Training System capability within the Awareness and Training family. > > — NIST SP 800-53 Rev. 5, Control AT-2(4) ### In plain English Provides literacy training to recognize suspicious communications and anomalous system behavior, using defined indicators of malicious code, to enhance early detection and response. In practice, this means you can prove you security system-level controls on a defined cadence. ## Why it matters SP 800-53 is the catalogue every U.S. federal authorisation (FedRAMP, FISMA, CMMC) and most regulated industries point at. A missing control surfaces as a Plan of Action & Milestones (POA&M) item that an Authorizing Official must approve before the Authority To Operate is granted or renewed. ## What an auditor looks for A 3PAO (FedRAMP) or Independent Assessor (NIST RMF) tests against NIST SP 800-53A assessment procedures. For each control they expect a documented implementation that addresses every assessment objective (Examine, Interview, Test) and an implementation summary in the System Security Plan. Within **Awareness and Training**, the assessor will trace your implementation back to the catalogue reference (Control AT-2(4)) and look for objective evidence on the latest two assessment cycles. ## How to implement #### Secure Development **Pipeline.** Require code review, SAST (Semgrep / Snyk Code), SCA (Dependabot / Renovate), secret-scanning and IaC scanning in the merge pipeline. **Branch protection.** Protected branches enforce reviews, signed commits and passing CI before merge; document the protection rules as the control evidence. #### Code Review Testing **Pipeline.** Require at least one human reviewer plus passing CI (lint, type, unit, security scan) before merge — protected branches enforce this. ### Operational checklist - **Security.** Document the trigger, the owner and the cadence. - **Detection.** Document the trigger, the owner and the cadence. - **Review.** Document the trigger, the owner and the cadence. - **Literacy.** Document the trigger, the owner and the cadence. - **Suspicious.** Document the trigger, the owner and the cadence. - **Scope:** system, application, review, capability, behavior, malicious code, response, security. ## Evidence to collect - **Code Repo Scan.** Source-control evidence — branch protection, required reviewers, CI status, SCA / SAST reports. Source control pipelines (GitHub, GitLab) enforce SDLC guardrails. Focus: Suspicious Communications And Anomalous System Behavior. ## Common pitfalls - CI security checks set to warn-only; the merge button is faster than the security feedback. ## How it maps to other frameworks Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit. - [**NIST SP 800-171 Rev. 3 3.14.2** — Malicious Code Protection](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-14-2-malicious-code-protection) - [**CIS Controls v8 16.12** — Implement Code-Level Security Checks](https://support.icompaas.com/compliance/cis-controls-v8/16-12-implement-code-level-security-checks) - [**ISO/IEC 27001:2022 A.8.28** — Secure coding](https://support.icompaas.com/compliance/iso-27001-2022/a-8-28-secure-coding) ## Related controls in NIST SP 800-53 Rev. 5 - [**Control AT-2(3)** — Social Engineering And Mining](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/at-2-3-social-engineering-and-mining) - [**Control CP-3(1)** — Simulated Events](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/cp-3-1-simulated-events) - [**Control MA-3** — Maintenance Tools](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/ma-3-maintenance-tools) - [**Control SC-7(9)** — Restrict Threatening Outgoing Communications Traffic](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-7-9-restrict-threatening-outgoing-communications-traffic) - [**Control SC-35** — External Malicious Code Identification](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-35-external-malicious-code-identification) - [**Control SC-3(3)** — Minimize Nonsecurity Functionality](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/sc-3-3-minimize-nonsecurity-functionality) ## References - [NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5](https://csrc.nist.gov/Projects/risk-management/sp800-53-controls) - Catalogue identifier: `Control AT-2(4)` Topics: application securityawareness trainingsecure developmentcode review testingdevsecopssecurity training ## Related compliance guidance - [NIST SP 800-53 Rev. 5: a practical implementation guide for cloud teams](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5): Start with the full NIST SP 800-53 implementation guide — scope, roadmap, evidence and how the assessment runs. - [NIST SP 800-171 and CMMC: a practical guide to protecting CUI in the cloud](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3): If your obligation is protecting CUI in your own systems for a federal or defence contract, this derived subset — not the full catalogue — is the requirement. - [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Most commercial SaaS already hold a SOC 2 Type 2, and FedRAMP 20x Class A is designed for providers that have one.