SI-3(10): Malicious Code Analysis

SI-3(10) requires you to analyze malicious code with defined tools and techniques so you can understand its characteristics and behavior, then feed what you learn back into detection, containment, and prevention. To operationalize it fast, establish a documented malware analysis workflow (triage → detonation → behavior review → IOCs → lessons learned), assign ownership, and retain repeatable evidence. ¹

Key takeaways:

• SI-3(10) is about analysis depth (behavior and characteristics), not just blocking malware at the perimeter. ²
• You need defined tools/techniques, triggers, and decision points so analysis happens consistently and produces actionable outputs. ¹
• Audit success depends on artifacts: case records, sandbox reports, IOCs, detection updates, and an end-to-end procedure tied to an owner. ²

The si-3(10): malicious code analysis requirement is a common sticking point because many organizations already run antivirus, EDR, and email security, yet still cannot show a consistent method for analyzing malicious code beyond basic detection. SI-3(10) focuses on what you do after you suspect or confirm malicious code: how you examine it, what tooling you use, what you learn (behavior, persistence, command-and-control patterns), and how those learnings change your defenses.

For a Compliance Officer, CCO, or GRC lead, the fastest path is to treat SI-3(10) as a mini-program inside your incident response and detection engineering functions. You need: (1) defined triggers for when code must be analyzed, (2) a standard analysis playbook that produces IOCs and defensive updates, (3) roles and escalation paths (including when you use a third party lab), and (4) durable evidence that proves the process runs repeatedly.

This page gives requirement-level implementation guidance you can hand to security operations, IR, and detection teams and then audit with confidence against NIST SP 800-53 Rev. 5. ¹

Regulatory text

NIST SI-3(10) excerpt: “Employ the following tools and techniques to analyze the characteristics and behavior of malicious code: {{ insert: param, si-03.10_odp }} ; and” ²

Operator interpretation: NIST expects you to define and use specific malware analysis tools/techniques (the control leaves the exact set to an organization-defined parameter) to understand both:

• Characteristics (file type, hashes, packing/obfuscation, exploited vulnerability, dropped artifacts), and
• Behavior (process tree, persistence, network callbacks, lateral movement attempts, encryption/credential theft actions).

Practically, you must decide what analysis methods you will apply, document them, and prove they are used when malicious code is encountered. ¹

Plain-English interpretation (what SI-3(10) really demands)

SI-3(10) requires a repeatable capability to take suspicious or confirmed malicious code and answer: What is it? What does it do? How does it get in? What should we block, detect, and eradicate now? The output is not the analysis report alone. The output is defensive change: updated detections, blocks, hardening tasks, and incident response steps grounded in observed behavior. ¹

If your team’s “analysis” is limited to “EDR quarantined it,” you will struggle to show conformance because SI-3(10) is explicitly about analyzing characteristics and behavior with defined tools/techniques. ²

Who it applies to (entity and operational context)

SI-3(10) is most directly applicable to:

• Federal information systems and programs assessed against NIST SP 800-53. ¹
• Contractor systems handling federal data, including environments where a third party processes, stores, or transmits federal information and commits to NIST controls by contract or authority-to-operate requirements. ²

Operationally, it applies where you have:

• Endpoints, servers, or cloud workloads that could execute untrusted code
• Email/web entry points for attachments and downloads
• CI/CD pipelines and software supply chain exposure (malicious packages, scripts, build artifacts)
• A SOC/IR function that must triage and respond to malware-like activity

It also applies to third parties you rely on for detection, managed response, malware detonation, or reverse engineering. You remain accountable for the control outcome even if analysis is outsourced.

What you actually need to do (step-by-step)

Use this as an implementation checklist you can convert into a procedure.

1) Name the control owner and define handoffs

• Assign a primary owner (usually SOC manager, IR lead, or threat intel lead).
• Define handoffs among SOC triage, IR, and detection engineering.
• Decide when you engage a third party (MDR, DFIR firm, malware lab) and how evidence is transferred.

Deliverable: SI-3(10) control implementation statement with named roles and escalation path. ¹

2) Define “triggers” that require malicious code analysis

Write explicit triggers so the process runs consistently:

• EDR alert on suspicious execution or persistence
• Suspicious attachment or macro detonation indicator
• Cloud workload spawning unusual processes
• Detection of known-bad hash, domain, or command line
• User report with suspicious executable/script

Deliverable: Triage decision tree that marks “send to analysis” conditions.

3) Choose your analysis tools/techniques and document the minimum set

Because the control uses an organization-defined parameter, you must define your set and keep it stable enough to audit. Typical categories:

• Static analysis (hashing, file metadata, strings, YARA-like pattern matching)
• Dynamic analysis (sandbox detonation, behavior tracing, network simulation)
• Memory/process analysis (process tree, injected threads, loaded modules) when relevant
• Network analysis (DNS/HTTP patterns, callbacks, TLS fingerprinting) when relevant

You do not need every technique for every sample. You do need documented criteria for selecting techniques by severity and exposure.

Deliverable: “Malicious Code Analysis Standard” listing approved tools/techniques and selection rules. ²

4) Build the workflow: intake → containment → analysis → outputs

A defensible workflow has clear stages:

A. Intake

• Capture sample safely (EDR isolate/export, email gateway artifact export, object storage copy).
• Preserve chain-of-custody where required by your incident handling policy.

B. Safety/containment

• Isolate affected host/workload as needed.
• Store samples in controlled repository with access logging.

C. Analysis

• Run static checks first to prevent unnecessary execution.
• Detonate in sandbox for behavioral logs (process, filesystem, registry/config, network).
• Identify persistence mechanisms and privilege escalation attempts.
• Extract IOCs (hashes, domains, URLs, mutexes, file paths, registry keys, scheduled tasks).

D. Outputs that must happen every time

• Update detections (EDR rules, SIEM queries, email gateway blocks, web proxy blocks).
• Feed IOCs into threat intel platform or equivalent tracking.
• Create/remediate tickets for hardening gaps (patches, macro policies, script control).
• Document scope checks (where else in environment the behavior/IOCs appear).

Deliverable: Playbook or SOP with required outputs and “done criteria.”

5) Tie it into incident response and change management

Auditors look for integration, not heroics:

• Ensure IR playbooks reference the malware analysis workflow.
• Ensure detection updates follow change control appropriate to your environment.
• Track “lessons learned” items to closure.

Deliverable: Cross-references between SI-3(10), IR procedures, and detection engineering backlog. ¹

6) Make it assessable: minimum logging, case management, and retention

Define where records live (ticketing system, IR platform, case management) and how long you retain:

• Malware analysis case record
• Sandbox report links/exports
• IOC list and where it was deployed
• Evidence of blocks/detections added and when

Deliverable: Evidence index (a simple spreadsheet works) mapping case IDs to artifacts.

Required evidence and artifacts to retain

Keep artifacts that prove both design (you have a defined method) and operation (you used it):

Design evidence

• SI-3(10) implementation statement (owner, scope, tools/techniques, triggers)
• Malicious code analysis SOP/playbook (version-controlled)
• Tool inventory/config summaries for analysis environment (sandbox, detonation VM templates, repositories)

Operational evidence (sample-based)

• A set of completed malware analysis cases showing the workflow
• Sandbox/dynamic analysis reports (PDF/JSON export or immutable link with access controls)
• IOC package produced from each case
• Proof of deployment: SIEM rule change, EDR detection update, firewall/DNS block ticket, email gateway policy update
• Post-incident notes tying analysis results to eradication steps

If you use a third party for analysis, retain the engagement record, report, and the internal tickets showing you implemented outputs.

Common exam/audit questions and hangups

Expect these questions in assessments aligned to NIST SP 800-53 Rev. 5:

• “Show your defined tools and techniques for malicious code analysis under SI-3(10).” ²
• “Provide evidence of malicious code analysis performed for recent events, including outputs.” ¹
• “How do you decide which samples get deeper analysis vs. basic triage?”
• “Where are IOCs stored, and how are they pushed into detections?”
• “How do you ensure analysis is performed safely and consistently?”
• “If a third party performs analysis, how do you govern quality and turnaround?”

Hangup pattern: teams can produce a sandbox screenshot but cannot show the downstream defensive changes. Treat “IOC-to-control deployment” as part of the requirement outcome.

Frequent implementation mistakes (and how to avoid them)

1. Relying on prevention tools as proof of analysis
   Avoidance: keep case records that show behavior review and resulting detection/block actions. ¹

2. No defined minimum technique set
   Avoidance: publish a short standard: what static checks are mandatory, when dynamic detonation is required, and who approves exceptions. ²

3. Analysis done, learnings not operationalized
   Avoidance: add “required outputs” to the playbook: IOC package + detection updates + scope hunt ticket.

4. Unsafe handling of samples
   Avoidance: restrict storage, isolate analysis environment, and document safe transfer methods.

5. Outsourced analysis with no internal ownership
   Avoidance: require internal review of third party reports and track remediation actions to closure.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so this page does not list enforcement actions.

Risk implications you can explain to leadership without overclaiming:

• Weak malicious code analysis increases dwell time because you cannot rapidly understand malware behavior and propagation paths. ¹
• Without analysis-driven IOCs and detection updates, you are more likely to miss related activity across endpoints, cloud workloads, and identities. ²
• Assessors can treat missing operational evidence as a control failure even if you have strong security tooling, because the requirement is about analysis actions and repeatable technique use. ¹

Practical execution plan (30/60/90-day)

Use this phased plan without treating timelines as a guarantee; compress or extend based on your operating model.

First 30 days (stand up the minimum viable SI-3(10))

• Assign owner and backups; document scope and triggers.
• Select and document the minimum tool/technique set (static + dynamic baseline).
• Publish a one-page workflow with required outputs (IOCs + detection/block updates).
• Identify where evidence will live (case management + artifact repository).
• Run the process on one recent sample (or a controlled test file) to produce a “golden” evidence set. ¹

By 60 days (make it repeatable and auditable)

• Convert workflow into an SOP/playbook with decision points and severity tiers.
• Integrate with incident response procedures and ticketing.
• Define third party engagement criteria and evidence requirements for outsourced analysis.
• Start a monthly evidence pull: select cases, verify artifacts, fix gaps.

By 90 days (mature the feedback loop)

• Formalize “IOC-to-deployment” SLAs internally (documented expectations, not stats).
• Add QA checks: confirm detection updates are active; confirm blocks are not expired unintentionally.
• Trend recurring malware families/initial access vectors and open hardening work items.
• Prepare an assessor-ready package: SOP + tool list + multiple case examples + evidence index. ²

How Daydream helps (earned, practical)

Most SI-3(10) failures are documentation and evidence failures, not lack of security tools. Daydream can help you map SI-3(10) to a named control owner, a step-by-step procedure, and recurring evidence artifacts so you can answer audits with a single, consistent control record and an evidence index that matches your workflow. ²

Frequently Asked Questions

What counts as “malicious code analysis” for SI-3(10)?

A repeatable process that examines both characteristics (what the code is) and behavior (what it does), using defined tools and techniques you document. You also need outputs that improve defenses, not just a report. ¹

Do we need reverse engineering for every sample?

No. Define tiers: basic static/dynamic analysis for most events, and deeper analysis (including reverse engineering or a third party lab) for high-impact or novel samples. Document the criteria and keep evidence of the decision. ²

If our MDR analyzes malware, are we compliant?

Potentially, but you still need governance and evidence: the MDR’s analysis deliverables plus internal tickets proving you deployed IOCs, updated detections, and remediated root causes. SI-3(10) is assessed on outcomes and repeatability. ¹

What evidence should we show an auditor first?

Start with the SOP/playbook and the defined tool/technique set, then provide several completed analysis cases with sandbox reports, extracted IOCs, and proof of detection/block updates. That sequence shows design and operation cleanly. ¹

How do we handle samples we can’t safely detonate?

Document an exception path: enhanced static analysis, controlled detonation in an isolated environment, or third party analysis. Record who approved the exception and what alternative techniques were applied. ²

How do we scope SI-3(10) in a cloud/SaaS-heavy environment?

Focus on the execution points you control: endpoints, cloud workloads, identity and email entry paths, and any pipelines that run third-party code. Then document what telemetry and artifacts you can collect from SaaS sources to support analysis. ¹

Footnotes

1. NIST SP 800-53 Rev. 5

2. NIST SP 800-53 Rev. 5 OSCAL JSON