SI-3(7): Nonsignature-based Detection

To meet the si-3(7): nonsignature-based detection requirement, you must deploy and operate malware and intrusion detection capabilities that do not rely only on known signatures, then prove they run effectively in your environment. Operationalize it by selecting behavior/heuristic/ML detections, tuning and monitoring them, and retaining evidence that detections trigger, escalate, and improve over time. ¹

Key takeaways:

• You need behavior-based (nonsignature) detection coverage, not just signature AV. ¹
• Auditors will look for continuous operation evidence: config, alerts, triage records, tuning history, and exceptions. ²
• The fastest path is to map SI-3(7) to an owner, a repeatable procedure, and recurring artifacts you can produce on demand. ¹

SI-3(7) is a common point of friction because many programs assume “we have antivirus” closes the gap. It does not. SI-3(7) asks for nonsignature-based detection, meaning your detection stack must find suspicious activity even when there is no known malware hash or signature to match. The practical test is simple: if an attacker uses a novel payload, a renamed tool, or a living-off-the-land technique, does your environment still generate actionable detection and response signals?

This requirement shows up in federal system security plans and contractor environments handling federal data, where NIST SP 800-53 Rev. 5 is used directly or as the basis for derived requirements. ² For a CCO or GRC lead, the goal is fast operationalization: define what “nonsignature detection” means in your stack, assign ownership, integrate with incident handling, and keep durable evidence. Done well, SI-3(7) becomes a measurable operations control instead of a paper policy. ¹

Regulatory text

Control: “NIST SP 800-53 control SI-3.7.” ¹

Operator interpretation of what you must do: implement malicious code protection capabilities with nonsignature-based detection and operate them as part of normal security monitoring. Your implementation must show (1) coverage where signature-based tools predictably fail, (2) an operating process to review detections and tune the system, and (3) evidence that it is enabled, monitored, and maintained. ²

Plain-English interpretation (what “nonsignature-based” means in practice)

Nonsignature-based detection is detection that does not depend on a pre-defined indicator such as a file hash, static signature, or known-bad pattern alone. In practice, this usually includes:

• Behavioral detections (process injection, credential dumping patterns, suspicious PowerShell, abnormal child processes)
• Heuristic rules (suspicious macro execution, unsigned binary execution in unusual paths)
• Reputation and anomaly signals (rare execution, first-seen binaries, unusual network beacons)
• EDR analytics that correlate events across endpoint telemetry

Your auditors are unlikely to care which vendor you chose. They will care that the control is real, operating, and demonstrably not limited to signature scanning. ²

Who it applies to

Entity scope

• Federal information systems implementing NIST SP 800-53 controls. ²
• Contractor systems handling federal data where NIST SP 800-53 controls are flowed down contractually or used as the governing baseline. ²

Operational context (where SI-3(7) is examined)

Expect this to be tested in environments with:

• Centrally managed endpoints (workstations and servers)
• Cloud workloads where agent-based or cloud-native telemetry feeds a detection platform
• Email/web ingress points where malicious code commonly enters
• A SOC or on-call security function that triages alerts

If you have isolated enclaves, OT, VDI, or “no agent allowed” systems, you still need a defensible alternative (network telemetry, application allowlisting, or compensating monitoring) plus documented exceptions. ²

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

Step 1: Assign ownership and define “done”

• Name a control owner (usually SecOps/Detection Engineering) and a GRC owner accountable for evidence readiness.
• Define the minimum “nonsignature detection” capabilities you will operate (behavioral/heuristic detections enabled; alerting routed to triage; tuning loop). ¹

Deliverable: a one-page control implementation statement you can paste into the SSP and hand to auditors.

Step 2: Inventory coverage targets and telemetry prerequisites

Create a scoped inventory:

• Endpoint populations (corporate endpoints, servers, privileged admin workstations)
• High-value assets (identity providers, jump hosts, CI/CD runners)
• Email/web gateways if they are part of your malicious code control stack

Then validate prerequisites:

• Endpoint logging/telemetry is enabled
• Time sync and asset identity are reliable (device names, user IDs)
• Alerts flow into a case/incident workflow

Deliverable: coverage matrix showing which platforms have which nonsignature detection controls enabled.

Step 3: Configure nonsignature detections in the tools you already own

Most organizations satisfy SI-3(7) via an EDR platform plus supporting controls. Configure:

• Behavioral prevention/detection modes (not “audit only” unless you can justify it)
• Cloud analytics features that flag suspicious behavior, not just known malware
• Alert routing to a monitored queue with severity and ownership

Deliverable: configuration screenshots/exports and an admin runbook for how detections are managed.

Step 4: Establish an alert handling and tuning loop

Write a short SOP that answers:

• Who reviews alerts and how often
• How you classify true positive vs false positive
• When you tune detection rules, add exclusions, or change severity
• When an alert becomes an incident and triggers incident handling

Keep it operational: name the ticketing system, the queue, and the on-call rota. ²

Deliverable: SOC SOP plus example tickets that show triage decisions and escalation.

Step 5: Test that nonsignature detections fire and are acted on

Run controlled tests that generate behavior-based detections (in an approved test environment or coordinated production test). Your goal is evidence that:

• The detection triggers
• The alert reaches the triage queue
• The responder follows the SOP
• The event is documented and closed with a disposition

Deliverable: test plan, approvals, alert screenshots, and resulting tickets.

Step 6: Manage exceptions and compensating controls

For systems that cannot run your endpoint tooling:

• Document the reason (technical limitation, vendor restriction)
• Define compensating monitoring (network-based detection, centralized logs, strict allowlisting)
• Record approval, review cadence, and expiration criteria for the exception

Deliverable: exception register entry tied to the asset inventory and risk acceptance workflow.

Step 7: Operationalize recurring evidence

Treat SI-3(7) like a continuous control with recurring artifacts:

• Monthly or quarterly detection health checks (agent coverage, alert pipeline)
• Periodic tuning reviews (top noisy rules, top high-severity detections)
• Tabletop or detection test evidence

This is where many teams fail: the tooling exists, but nobody can prove it stayed enabled and effective. ¹

Required evidence and artifacts to retain (audit-ready)

Use this as your evidence checklist:

• Control ownership record (RACI or control register entry) ¹
• Tooling architecture diagram showing where nonsignature detection happens (EDR, email, network)
• Configuration evidence: exports or screenshots showing behavioral/heuristic settings enabled
• Coverage reports: endpoint agent deployment/health, protected workload list
• Alert samples: representative behavior-based alerts (redact as needed)
• Triage records: tickets/cases with timestamps, analyst notes, disposition, escalation where required
• Tuning/change history: rule changes, exclusions, approvals, and rationale
• Test artifacts: detection test plan, approvals, results, remediation actions
• Exceptions: risk acceptance, compensating controls, review/expiration

If you use Daydream to map SI-3(7) to the control owner, procedure, and recurring artifacts, you reduce the scramble factor during assessments because the evidence list becomes a standing request queue rather than a one-off project. ¹

Common exam/audit questions and hangups

Auditors and assessors tend to probe in predictable ways:

• “Show me that detection is nonsignature-based, not just signature AV.” Bring configuration proof and example alerts that are behavior-driven. ²
• “How do you know it’s running everywhere?” Expect to show an agent coverage/health report and your asset inventory mapping.
• “Who reviews alerts and what happens next?” Produce the SOP and a sample of closed tickets.
• “How do you prevent alert fatigue from becoming ‘ignore everything’?” Show tuning governance and a feedback loop with change control.
• “What about systems that cannot support the agent?” Show exceptions and compensating controls, tied to specific assets.

Frequent implementation mistakes (and how to avoid them)

Mistake	Why it fails	How to avoid
Treating SI-3(7) as “we have AV”	Signature-only tools miss novel techniques; auditors will ask for nonsignature evidence	Document and enable behavioral/heuristic features and show behavior-based alerts 2
Running detections in “monitor only” forever	Creates a paper control with no operational consequence	Define when to block vs alert; require documented rationale for non-enforcement
No tuning governance	False positives lead to disabled rules or ignored alerts	Add approvals for exclusions and maintain a tuning log tied to tickets
Weak evidence hygiene	You cannot prove continuous operation	Predefine recurring artifacts and collect them routinely 1
Exceptions are informal	“We can’t install agents” becomes a blind spot	Formal exception register with compensating controls and review criteria

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so you should not expect a ready-made case cite. Your risk argument should stay grounded in operational impact: nonsignature detection reduces dwell time for novel malware and behavior-based tradecraft, and it materially affects incident detection and response quality. Tie SI-3(7) to your broader monitoring and incident handling narrative in NIST SP 800-53 programs. ²

Practical 30/60/90-day execution plan

First 30 days (stabilize scope and prove “enabled”)

• Assign control owner and document the SI-3(7) implementation statement. ¹
• Build an asset-to-coverage matrix for endpoints, servers, and key cloud workloads.
• Confirm behavioral/heuristic detection settings are enabled and alerts route to triage.
• Start an evidence folder structure and begin collecting configuration exports and coverage reports.

Days 31–60 (make it operational)

• Publish the alert triage SOP (intake, disposition, escalation).
• Create a tuning/change workflow for detection rules and exclusions.
• Collect representative alert-to-ticket samples that demonstrate analyst action.
• Formalize exception handling for systems without agents.

Days 61–90 (prove effectiveness and repeatability)

• Run at least one controlled detection test and retain artifacts (approvals, alerts, tickets, lessons learned).
• Add recurring reporting (detection health, coverage drift, top alert drivers).
• Run an internal “mock audit” for SI-3(7): can you produce evidence within the same business day, without heroics?

Frequently Asked Questions

What counts as “nonsignature-based” for SI-3(7)?

Behavior-based, heuristic, reputation, or analytics-driven detection qualifies if it can detect suspicious activity without a known signature match. You must be able to show configuration and alert examples that demonstrate this. ²

Can EDR alone satisfy the si-3(7): nonsignature-based detection requirement?

Often yes, if EDR behavioral detections are enabled, centrally monitored, and tied to an incident workflow. You still need to address coverage gaps (email/web/network) and exceptions where EDR cannot be deployed. ²

What evidence is most persuasive to auditors?

A short implementation statement, configuration exports showing behavior/heuristic features enabled, coverage/health reports, and alert-to-ticket samples with tuning history. Evidence that repeats over time is stronger than one-time screenshots. ¹

How do we handle systems that cannot run an endpoint agent?

Use a formal exception with a documented reason, compensating monitoring (for example, network telemetry or strict allowlisting), and an approval and review process tied to the specific assets. Keep the exception register current. ²

Do we need to block malware automatically to meet SI-3(7)?

SI-3(7) focuses on detection capability; blocking may be appropriate but is not the only acceptable outcome. If you choose alert-only modes, document why and show timely triage and escalation. ²

How can Daydream help without turning this into a documentation exercise?

Use Daydream to assign SI-3(7) ownership, store the operating procedure, and schedule recurring evidence pulls (coverage reports, sample tickets, tuning logs). That structure supports real operations and reduces assessment churn. ¹

Footnotes

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

2. NIST SP 800-53 Rev. 5