SC-4 asks you to prevent unauthorized and unintended information transfer through shared system resources. In plain terms, when memory, disk blocks or a cache are released and given to someone else, the new user must not see what the old one left there.
NIST notes this is also called object reuse and residual information protection. 800-53 binds federal systems and contractors. Everyone else can use it to answer multi tenant and shared hosting questions.
What it means in practice
The record is careful about scope. The control covers information produced by prior users or processes, including encrypted representations of it. It does not address information remanence on deleted media, covert channels, or the like. Those are handled elsewhere.
Where it shows up for a software company is multi tenant services. Memory pages, temp files, caches, connection pools and queues are all shared resources. If tenant B can ever see leftovers from tenant A, that is an SC-4 failure.
Evidence to collect
- A description of shared resources in your platform and how each is cleared or isolated.
- Test results, such as a tenant isolation test that writes data as one tenant and tries to read it as another.
- Cloud provider documentation for the layers you do not control, such as hypervisor memory scrubbing.
- Code review notes on cache keys and temp file handling.
Common gaps
Cache keys that omit the tenant identifier. Temp directories reused across jobs without cleanup. Shared build agents that keep workspaces from the last run.
How to implement it
Zero or recreate buffers on release. Include tenant and user in every cache key. Give each job a clean workspace. Add an automated cross tenant test to your release pipeline, and keep the results.
The enhancements, SC-4(1) Security Levels and SC-4(2) Multilevel or Periods Processing, apply to classified style environments and rarely to commercial teams.
Quick check
Name another term for what SC-4 covers.
Object reuse, also called residual information protection.
