Ransomware attempt on a clinic workstation
EDR blocks execution, isolates the host, and opens an IR ticket; ePHI file encryption is prevented — SI-3 detection actioned.
Malicious Code Protection
High Risk
Moderate
Medium Cost
SI-3 requires implementing malicious code protection at system entry and exit points and on system components, updating protections when new releases are available, configuring to perform periodic and real-time scans as defined, and addressing the results of malicious code protection detections. Ransomware and trojans remain primary threats to care delivery and ePHI confidentiality; SI-3 is the baseline malware defense layered with application allowlisting and EDR where risk warrants.
Control Objective
Detect, block, and respond to malicious code on ePHI-related endpoints and servers with current signatures/engines, defined scanning, and actioned alerts.
Implementation Guidance
- Deploy enterprise antimalware/EDR on workstations, servers, and jump hosts in scope; document exceptions for appliances that cannot run agents.
- Enable real-time protection and scheduled full scans during maintenance windows for clinical devices that support them.
- Centralize update and health reporting; alert on stale definitions or missing agents.
- Define response playbooks for detections (IR-4): isolate, preserve, eradicate, recover.
- Scan inputs at key entry points: email gateways, web proxies, and file upload portals.
- Restrict local admin to reduce malware persistence; pair with SI-2 patching.
- Review quarantined/detected malware trends monthly for targeting of healthcare apps.
- Cover VDI and cloud golden images — not only physical PCs.
Real-World Use Cases
How this control shows up in healthcare and HIPAA-covered environments.
Stale antivirus on a neglected EHR interface server
Health dashboard shows 14 days without updates; automated ticket forces remediation before audit sampling.
Malicious macro in a billing spreadsheet emailed to staff
Gateway detonation + endpoint block stop the payload; awareness follow-up issued under AT-2.
Best Practices
- Ubiquitous coverage with health monitoring.
- Real-time + scheduled scanning policy.
- Fast response playbooks.
- Email/web entry-point scanning.
- Minimize exclusions; justify clinical exceptions.
- Include VDI/cloud images.
Common Gaps & Violations
- Servers 'excluded for performance' without risk acceptance.
- Consumer AV on unmanaged clinic PCs.
- Alerts ignored (alert fatigue).
- Definitions months out of date.
- Medical devices on flat LAN with no compensating malware controls at the boundary.
Required Documentation
- Malicious code protection standard
- Agent deployment / coverage reports
- Update and scanning configuration baselines
- Exception register with compensations
- Detection response playbook and sample tickets
How to Test & Validate
- Sample endpoints/servers for active up-to-date agents.
- Verify real-time protection settings on a workstation build.
- Confirm email gateway malware scanning is enabled.
- Review recent detections for IR follow-through.
- Validate exceptions are documented and time-bounded.
Audit Considerations
Malware protection is table stakes in HIPAA technical evaluations. Missing agents on ePHI servers and unmanaged alerts are common findings.
HIPAA Mapping
How this NIST control supports HIPAA Security Rule expectations.
- 164.308(a)(5)(ii)(B) Protection from Malicious Software — procedures for guarding against, detecting, and reporting malicious software.
- 164.308(a)(1) Risk Management — malware/ransomware are material risks to ePHI availability and confidentiality.
- 164.312(a) Access Control — malware often subverts access controls; endpoint protection supports them.
- 164.308(a)(6) Incident Procedures — malware detections must feed incident response.
Compliance Tips
- Report 'missing/stale agent' as a weekly KPI to IT leadership.
- Never broadly disable AV on EHR servers without AO-accepted residual risk and compensations.
- Test restore paths — SI-3 blocks are not a substitute for tested backups (CP-9).
Frequently Asked Questions
Is EDR required for SI-3?
SI-3 requires malicious code protection; modern EDR often best meets detection/response needs, but configure whatever you deploy to update, scan, and alert.
How does SI-3 relate to SI-2?
SI-2 is flaw remediation/patching; SI-3 is malware defense. Ransomware often needs both.
What about immutable medical devices?
Segment them, control media/USB, scan upstream, and monitor — document why agents cannot run.
References & Resources
- NIST SP 800-53 Rev. 5 — SI-3
- NIST SP 800-83 Malware Incident Prevention
- Related controls: SI-2, SI-4, IR-4, AC-17, MP-7
Related Guidelines
Related controls that commonly accompany SI-3.
Need Help Implementing SI-3?
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