Hospital ransomware advisory
ISAC releases indicators for a new encryptor; SC-35 process pushes hashes to EDR within hours and hunts for footholds on clinical jump hosts.
External Malicious Code Identification
High Risk
Moderate
Medium Cost
SC-35 includes external indicators of malicious code from organization-defined sources and acts on them to eradicate or quarantine code and update protections. Healthcare SOCs consume ISACs, vendor intel, and national alerts to block ransomware families targeting hospitals before signatures hit every endpoint organically.
Control Objective
Ingest external malicious-code indicators from trusted sources and operationalize them to protect systems that create, receive, maintain, or transmit ePHI.
Implementation Guidance
- Subscribe to healthcare-relevant intel (ISAC, vendors, CISA alerts).
- Automate indicator ingest into EDR/SIEM/email gateway where quality allows.
- Define action playbooks: block, hunt, patch priority.
- Vet indicator quality to limit false positives on clinical workflows.
- Share sanitized lessons with BAs when outbreaks affect common vendors.
- Measure time-from-intel-to-control-update.
- Pair with SI-3 malicious code protection on endpoints.
- Document sources and review quarterly.
Real-World Use Cases
How this control shows up in healthcare and HIPAA-covered environments.
Malicious EHR phishing kit
External intel identifies credential-harvest domains; email and DNS controls block them before payroll-themed lures hit clinicians.
Vendor supply-chain warning
Alert on trojanized clinical software update drives CM-14 verification and temporary install freeze.
Best Practices
- Healthcare-relevant intel sources.
- Automated high-confidence ingest.
- Playbooks for block/hunt.
- Tune for clinical false positives.
- Measure latency to action.
- Coordinate with SI-3/SI-4.
Common Gaps & Violations
- Intel email newsletter never operationalized.
- Blindly blocking indicators that break vendor update domains.
- No owner for intel pipeline.
- Ignoring sector-specific advisories.
- Claiming SC-35 with only antivirus defaults.
Required Documentation
- External malicious code intel standard (SC-35)
- Source list and SLAs
- Ingest/automation architecture
- Action playbooks
- Sample intel-to-block tickets
How to Test & Validate
- Trace a recent advisory to a control change ticket.
- Verify indicators present in EDR/gateway.
- Review false-positive handling.
- Confirm source list currency.
- Measure median time-to-enforce for last 5 high-severity items.
Audit Considerations
SC-35 is the intel-to-action loop. Assessors want sources plus evidence you acted—not unread PDF advisories.
HIPAA Mapping
How this NIST control supports HIPAA Security Rule expectations.
- 164.308(a)(5) Security Awareness — threat awareness informed by external intel.
- 164.308(a)(1) Risk Management — timely response to emerging malware threats.
- 164.308(a)(6) Incident Response — intel supports detection and eradication.
- 164.312(a)/(c) — technical safeguards updated against known malicious code.
Compliance Tips
- Assign an intel owner in the SOC roster.
- Prefer STIX/TAXII or API feeds into EDR.
- Report intel response time to leadership.
Frequently Asked Questions
Is antivirus enough for SC-35?
AV is SI-3 territory; SC-35 emphasizes incorporating external indicators and acting on them.
Which sources are required?
Organization-defined—healthcare ISAC plus vendor/CISA feeds are common.
Related to SI-4?
SI-4 monitors systems; SC-35 feeds external malicious-code identification into protective actions.
References & Resources
- NIST SP 800-53 Rev. 5 — SC-35
- Related controls: SI-3, SI-4, IR-4, SC-7
Related Guidelines
Related controls that commonly accompany SC-35.
Need Help Implementing SC-35?
Our auditors map NIST SP 800-53 controls to your HIPAA Security Rule program — policies, technical evidence, and audit readiness.