SC-3: Security Function Isolation

To meet the sc-3: security function isolation requirement, you must design your systems so security controls (for example, logging, access control, malware protection, monitoring) run in segregated, protected contexts that ordinary applications and users cannot tamper with. Operationalize SC-3 by defining “security functions,” enforcing isolation through architecture and configuration, and retaining proof that isolation is designed, implemented, and tested. ¹

Key takeaways:

• SC-3 is about preventing nonsecurity code, admins, and workloads from disabling or modifying security controls. ²
• Isolation is achieved through layered technical measures (privilege boundaries, segmentation, hardened hosts, protected logging/monitoring planes), not a policy statement.
• Auditors look for system-specific implementation detail and repeatable evidence that isolation works in practice, including test results and configuration baselines.

SC-3 is a deceptively short control with real engineering consequences: “Isolate security functions from nonsecurity functions.” ² For a Compliance Officer, CCO, or GRC lead, the fast path is to translate that sentence into an enforceable scope statement (what counts as a security function in your environment), an architectural pattern (where those functions run), and evidence (how you prove nonsecurity workloads cannot interfere).

In practice, SC-3 is where security tooling fails quietly. If endpoint protection can be stopped by a local admin, if audit logs can be edited by the application team, if your SIEM collector shares a host with app code, or if a CI/CD runner can change policy-as-code without gatekeeping, you have isolation gaps. SC-3 also intersects with third-party risk: managed service providers, SaaS admins, and outsourced IT often have powerful access paths that can accidentally defeat isolation unless you design for it.

This page gives requirement-level implementation guidance you can execute: applicability, step-by-step actions, required artifacts, common audit hangups, and a practical execution plan.

Regulatory text

Requirement (verbatim): “Isolate security functions from nonsecurity functions.” ²

Operator interpretation (what you must do):

• Identify which components in your environment perform security functions (prevent, detect, respond, recover).
• Implement technical isolation boundaries so nonsecurity functions (business apps, developer tools, user workloads, standard admin activity) cannot disable, alter, bypass, or materially degrade those security functions.
• Demonstrate isolation through architecture decisions, configuration, access controls, and testing evidence, not intent statements. ¹

Plain-English interpretation

SC-3 means: security controls must be harder to tamper with than the systems they protect.

If an attacker compromises a workload, a developer account, or a standard admin path, they should not be able to:

• turn off endpoint protection or EDR,
• edit/delete security logs,
• modify detection rules without review,
• alter security policy enforcement points,
• stop monitoring agents or redirect telemetry,
• change IAM guardrails that constrain the environment.

Isolation can be physical (separate hosts), logical (separate accounts/projects/tenants), privilege-based (separate roles), and network-based (separate management plane). The right answer is usually a combination.

Who it applies to (entity and operational context)

SC-3 applies most directly when you align to NIST SP 800-53 Rev. 5 for:

• Federal information systems, and
• Contractor systems handling federal data (for example, regulated government contractors and service providers). ²

Operationally, you should treat SC-3 as in-scope anywhere you have:

• shared infrastructure hosting both security tooling and production workloads,
• centralized logging/monitoring,
• CI/CD pipelines that can change security configurations,
• admins (including third parties) with broad access,
• cloud control planes (AWS/Azure/GCP) where policy misconfiguration can disable guardrails,
• endpoints where users or local admins might disable protections.

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

Step 1: Define “security functions” for your environment

Create a short, explicit inventory of security functions, mapped to real components. Example categories:

• Identity & access enforcement: IAM policy engines, SSO, MFA, PAM.
• Telemetry and audit: OS/audit logging, application security logs, SIEM collectors, log archives, time sync.
• Threat prevention/detection: EDR agents, email security, WAF, IDS/IPS, CSPM/CIEM.
• Security administration: key management, secrets management, vulnerability scanning, config compliance tooling.
• Response tooling: SOAR, case management, containment automation.

Deliverable: a “Security Functions Register” tied to systems, owners, and where each function runs.

Step 2: Draw your isolation boundaries (diagram first, then controls)

For each security function, document:

• where it runs (host/service/account/tenant),
• what it depends on (network, identity, storage),
• who administers it,
• what could disable it.

Then pick an isolation pattern:

• Separate management plane: security tooling runs in a dedicated admin subnet/VPC/VNet and/or dedicated cloud account/subscription.
• Separate identity plane: restricted admin roles for security systems; no shared accounts; break-glass controlled.
• Separate compute plane: do not co-host security collectors/controllers on app servers where feasible.
• Separate data plane: append-only or WORM-like log storage; restrictive delete permissions.

Deliverable: an “SC-3 Isolation Architecture” diagram and narrative, per major environment (on-prem, cloud, endpoints).

Step 3: Enforce privilege separation for security administration

Implement concrete access rules:

• Security tool admin roles are limited to the security team (or formally delegated staff) and gated by approvals.
• Application operators do not have direct permission to disable security agents, delete logs, or change detection content.
• Third-party admin access is constrained by role, time bounds, and session monitoring.

Evidence should show role definitions, membership, and the approval path for changes.

Step 4: Isolate logging and monitoring from the workloads being monitored

This is a frequent audit focus because log tampering erases forensic trail. Minimum operational expectations:

• Logs ship off-host to a central collector where app workloads do not have admin rights.
• Log storage has restrictive delete permissions and retention controls.
• Security monitoring rules/configs have change control, ideally with code review and audit trails.

Deliverable: logging architecture diagram + permissions snapshots + sample immutable/audited change history.

Step 5: Harden endpoints and servers so users cannot disable security controls

Common isolation measures:

• Endpoint protections run with tamper protection and require elevated, controlled credentials to disable.
• Servers enforce configuration baselines; local admin rights are controlled and monitored.
• Security agents are deployed and monitored for health; alerting triggers if an agent stops reporting.

Deliverable: endpoint/server hardening standard + sample device configuration + alert/runbook for agent failure.

Step 6: Build isolation into CI/CD and configuration management

If your pipelines can change security policy, they are part of the isolation boundary:

• Separate repos/branches for security policy-as-code with mandatory review.
• Separate CI runners for security code; no shared credentials with application pipelines.
• Store secrets in a dedicated secrets manager with least-privilege retrieval.

Deliverable: repo protection settings, pipeline role permissions, and change tickets/approvals.

Step 7: Test the isolation (prove tamper resistance)

Create repeatable tests that demonstrate:

• a standard app operator cannot disable EDR,
• a compromised workload cannot delete central logs,
• nonsecurity admins cannot change SIEM rules without going through change control,
• third-party accounts cannot access security admin planes beyond their role.

Deliverable: SC-3 test plan + test results + remediation tickets for failures.

Step 8: Assign ownership and set recurring evidence

SC-3 fails in audits when nobody “owns” it.

• Name a control owner (often Security Architecture or SecOps).
• Define evidence cadence aligned to your assessment rhythm (for example, per release, per quarter, or per major change).

Daydream fits here as the control system of record: map SC-3 to the owner, implementation procedure, and the recurring evidence artifacts so you can answer assessor questions quickly with consistent proof. ²

Required evidence and artifacts to retain (audit-ready)

Keep artifacts system-specific. Auditors reject generic policies without implementation proof.

Evidence	What it proves	Example artifacts
Security Functions Register	You defined “security functions” in scope	Inventory spreadsheet/export, CMDB mapping, owners
Isolation architecture documentation	You designed isolation intentionally	Network/account diagrams, data flow diagrams, boundary narratives
Access control evidence	Nonsecurity roles cannot administer security functions	IAM role listings, group membership, PAM role assignments, approvals
Logging isolation evidence	Workloads cannot tamper with logs	Central logging config, storage permissions, retention settings
Configuration baselines	Standard builds enforce separation	CIS-like hardening baselines, GPO/MDM profiles, server templates
Change control records	Security config changes are controlled	Tickets, pull requests, approvals, audit logs
SC-3 test results	Isolation works in practice	Test scripts, screenshots, command output, findings, remediations
Third-party access constraints	External admins cannot bypass isolation	Contracts/SOW access clauses, time-bound access logs, session recordings references

Common exam/audit questions and hangups

Expect these questions:

• “List your security functions. Where do they run, and who can administer them?”
• “Can a system admin or developer disable endpoint protection or logging?”
• “Show me that production application teams cannot delete or modify SIEM logs.”
• “How do you protect detection logic and alerting rules from unauthorized changes?”
• “What happens if a third party with admin access goes rogue or is compromised?”
• “Show testing that validates isolation, and show remediation for failures.”

Hangups that stall audits:

• Confusing segmentation with isolation. Segmentation helps, but privilege boundaries and admin separation usually decide the outcome.
• Assuming cloud provider controls automatically satisfy isolation. Assessors still want to see your tenant/account design and permissions.
• No evidence that the control is operating. Design docs without tests or access listings are a common failure mode.

Frequent implementation mistakes and how to avoid them

1. Security tooling runs on the same hosts as production workloads.
   Fix: move collectors/controllers to dedicated hosts/accounts; restrict inbound management access.

2. Shared admin groups (Domain Admins / cloud subscription Owners) manage both apps and security tools.
   Fix: split roles; introduce PAM; require approvals for security admin actions.

3. Logs can be deleted by app operators “for troubleshooting.”
   Fix: centralize logs; enforce least privilege; define a break-glass process with explicit approval and audit trail.

4. EDR/agent health is assumed.
   Fix: alert on missing telemetry; require remediation workflow when endpoints stop reporting.

5. CI/CD can modify security policy without controls.
   Fix: separate pipelines and credentials; require code review; restrict merge rights.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so you should treat SC-3 primarily as an assessment and breach-resilience control rather than a control with a specific published penalty trail in this dataset. The risk is practical: if security functions are not isolated, a compromise often escalates into “security blindness” (monitoring disabled, logs altered, detections bypassed), which increases impact and complicates incident response and reporting.

Practical 30/60/90-day execution plan

First 30 days (stabilize scope and visibility)

• Appoint an SC-3 control owner and backups.
• Build the Security Functions Register for your most critical environments first (production, identity, logging). ²
• Produce current-state diagrams showing where security tooling runs and who administers it.
• Identify top isolation gaps: shared admin roles, co-hosted security tooling, log deletion permissions, endpoint tamper controls.

Days 31–60 (implement high-impact isolation changes)

• Separate security admin roles from nonsecurity operations; implement PAM or equivalent gated admin workflows.
• Move or segregate central logging/SIEM ingestion and storage so production workloads cannot modify it.
• Lock down detection content changes (SIEM rules, EDR policies) through change control and code review.
• Add alerting for loss of telemetry and for changes to security configuration objects.

Days 61–90 (prove it, then make it repeatable)

• Execute SC-3 tests (attempt to stop agents, delete logs, change rules as nonsecurity roles) and document outcomes.
• Remediate failures and track to closure with tickets and post-change validation.
• Set the recurring evidence rhythm and store artifacts in your GRC system. Daydream can track the SC-3 procedure, owners, and evidence checklist so audits don’t turn into a scavenger hunt. ²

Frequently Asked Questions

What counts as a “security function” under SC-3 in a modern cloud stack?

Treat any control that enforces access, generates audit records, detects threats, or supports response as a security function. If disabling it would reduce your ability to prevent/detect/respond, include it in scope and isolate it. ¹

Does network segmentation alone satisfy SC-3?

Usually no. Segmentation helps reduce reachability, but SC-3 also requires privilege and administrative isolation so nonsecurity roles cannot disable or modify security controls through authorized channels.

How do I show evidence that nonsecurity admins cannot delete logs?

Provide permissions from the logging storage and the roles/groups that can administer it, plus sample audit events for configuration changes and deletions (or proof deletions are blocked). Pair that with an architecture diagram showing off-host log forwarding.

We use a third party MSSP. How does SC-3 apply?

The MSSP is part of your isolation design. Define what security functions they administer, constrain their access with least privilege and time-bound workflows, and retain evidence of access approvals and activity logs.

What’s the minimum testing needed for SC-3?

Run negative tests aligned to your threat model: attempt to disable agents, stop logging, alter detection rules, and delete central logs using nonsecurity roles. Keep the test plan, results, and remediation records.

Where does Daydream help specifically with SC-3?

Daydream helps you map SC-3 to a named owner, a written implementation procedure, and a recurring evidence checklist so you can answer assessor questions with consistent, system-specific artifacts. ²

Footnotes

1. NIST SP 800-53 Rev. 5

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