Process Isolation SC-39
System and Communications Protection · Low baseline ✗ Not implemented
Status — program-wide
What references this control
No risks name this control in their Framework field yet.
No policies reference it yet.
Link a risk or policy to this control
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Source: NIST SP 800-53 Rev.5, System and Communications Protection family NIST SP 800-53 Rev.5. The baseline shows the lowest SP 800-53B baseline (Low / Moderate / High) this control appears in NIST SP 800-53B.
Control guide — plain-English, per NIST SP 800-53
SC-39 (Process Isolation) is about keeping each running process in its own execution domain — its own private slice of memory — so one process cannot read or corrupt another’s. On a modern operating system the kernel and the CPU (Central Processing Unit) provide most of this for free; the work is keeping those protections switched on and not weakening them. It is a foundational System and Communications Protection control that applies from the Low baseline up.
What good looks like
- Rely on the separation the operating system already gives you — a separate virtual address space per process — and do not turn it off.
- Keep the hardware memory protections on: ASLR (Address Space Layout Randomization) so memory locations are unpredictable, and NX / DEP (No-eXecute / Data Execution Prevention) so data regions cannot run as code.
- Run each service under its own least-privilege account, so a compromised process is boxed into one identity.
- Add extra domains where the risk warrants it — sandboxing or systemd confinement for internet-facing or risky services.
- Keep the kernel patched — isolation failures are usually kernel bugs.
Framework mapping
- NIST CSF 2.0 — PR.DS-10 — The confidentiality, integrity, and availability of data-in-use are protected
How to move it toward Implemented
- Confirm ASLR is fully on:
sysctl kernel.randomize_va_spaceshould return2; pin it in a file under/etc/sysctl.d/. - Give each network service its own non-root user and check it with
systemctl show -p User <service>orps -eo user,comm. - Confine exposed services with systemd directives —
NoNewPrivileges=true,PrivateTmp=true,ProtectSystem=strict, andProtectHome=true— then score the result withsystemd-analyze security <service>. - Keep the kernel current (for example, review
apt list --upgradableforlinux-imageupdates on a set cadence). - Attach the sysctl settings and the
systemd-analyze securityoutput as hardening evidence on the asset, namingSC-39in the Requirement field — that moves it from ‘To assess’ toward ‘Completed’.