System and Communications Protection 3.13.4 (3.13.4)
Prevent unauthorized and unintended information transfer via shared system resources.
Get Full GuidanceWhat Is This CMMC Control?
This control requires organizations to ensure that when system resources (like memory, storage, or processing components) are released from one user or process and assigned to another, no leftover data from the previous user remains accessible. This prevents sensitive information from being inadvertently exposed to unauthorized users who later use the same system resources.
Control Intent
Prevent unauthorized disclosure of CUI through residual data remaining in shared system resources after they are released and reallocated to different users or processes.
Who This Control Applies To
- •Multi-user systems where resources are shared between different users or security contexts
- •Virtual environments where multiple tenants or workloads share underlying hardware resources
- •Systems with shared memory, storage, or processing components that handle CUI
- •Cloud-based systems where compute, storage, or memory resources are dynamically allocated
- •Terminal servers, virtual desktop infrastructure (VDI), and shared workstation environments
- •Database systems where memory buffers are reused across different queries or users
Not Applicable When
- •Single-user systems with no resource sharing between different security contexts
- •Dedicated physical systems with no multi-tenancy or resource sharing
- •Systems that never process, store, or transmit CUI
- •Air-gapped systems with only one user account and no process isolation requirements
Key Objectives
- 1Ensure system resources are properly cleared or overwritten before being reallocated to prevent information leakage
- 2Protect against unauthorized access to residual data in shared memory, storage, and processing resources
- 3Prevent unintended information transfer between users or processes sharing system resources
Sample Self-Assessment Questions (Partial)
Does your system share computing resources (memory, storage, processing) between different users or processes?
Are you using virtual machines, containers, or cloud infrastructure where resources are dynamically allocated?
Implementation Approaches (High-Level)
Operating System Memory Zeroing
Configure operating systems to automatically zero or scrub memory pages before reallocating them to different processes or users
Hypervisor Memory Sanitization
Configure virtualization platforms to clear memory pages between virtual machine instances and prevent cross-tenant information leakage
Database Buffer Pool Management
Configure database systems to clear buffer pools, temporary tables, and query caches to prevent residual data exposure between sessions or queries
Secure Temporary File and Swap Space Management
Configure systems to securely clear temporary files, swap space, and page files to prevent residual CUI exposure
Application-Level Memory Clearing
Implement secure coding practices to explicitly clear sensitive data structures, encryption keys, and buffers from application memory
Container and Orchestration Platform Isolation
Configure container runtimes and orchestration platforms to isolate and clear shared kernel resources between containers
Evidence & Assessment Notes
Expected Evidence
Organizations should maintain documentation and evidence demonstrating compliance with this control. This may include policy documentation, configuration records, audit logs, access reviews, and other relevant artifacts that show how the control is implemented and maintained.
Plan of Action & Milestones (POA&M)
If memory clearing is not currently enabled, create a POA&M to implement operating system-level memory zeroing or scrubbing across all systems in scope within 90-180 days For virtualized environments without hypervisor memory sanitization, develop a POA&M to configure and validate memory clearing controls within 120 days If database buffer pools are not properly managed, create a POA&M to implement buffer clearing procedures and encryption within 90 days For systems with unencrypted swap space or page files, develop a POA&M to implement encryption or clearing mechanisms within 60-90 days If applications do not implement secure memory clearing, create a POA&M for code remediation and developer training within 180 days, prioritizing applications processing the most sensitive CUI For container environments without adequate isolation, develop a POA&M to implement kernel-level resource isolation and clearing controls within 120 days If relying on cloud service providers without verified sanitization controls, create a POA&M to obtain contractual assurances or technical validation within 60 days Prioritize POA&M items based on the sensitivity of CUI processed and the likelihood of multi-tenancy or resource sharing Include testing and validation activities in POA&M milestones to confirm effectiveness of implemented controls Consider compensatory controls such as dedicated systems or enhanced encryption while permanent solutions are implemented
Frequently Asked Questions
What is the difference between this control (3.13.4) and media sanitization (3.8.3)?
Control 3.13.4 addresses clearing data from shared system resources (memory, cache, buffers) during normal operations when resources are reallocated between users or processes. Control 3.8.3 addresses sanitization of storage media when it is being disposed of, reused outside the organization, or released from CUI processing. This control focuses on runtime memory management, while 3.8.3 focuses on end-of-life media handling.
Does this control require clearing memory after every single process or only when switching between different users?
This control requires clearing shared resources when they are released and reallocated, regardless of whether the reallocation is to the same user or a different user. The key concern is preventing unauthorized access to residual data, which can occur even within the same user's context if different security levels or applications are involved. Operating system and hypervisor-level controls typically handle this automatically for all reallocations.
Are cloud service providers responsible for implementing this control, or is it the customer's responsibility?
Responsibility depends on the cloud service model. For IaaS, the provider typically handles hypervisor-level memory sanitization, but the customer is responsible for OS and application-level controls. For PaaS and SaaS, the provider generally implements all resource sanitization controls. Customers must verify provider controls through attestations, contracts, or technical validation and document the shared responsibility model.
How can we verify that memory clearing controls are actually working and not just configured?
Verification requires technical testing such as memory forensics, attempting to read deallocated memory regions, or using specialized tools to detect residual data. Assessors may review test results, validation reports, or vendor documentation confirming effectiveness. For inherited controls (OS, hypervisor, cloud provider), attestations or third-party audit reports may provide sufficient evidence of proper implementation.
Does encrypting data at rest satisfy this control's requirement for clearing shared resources?
Encryption at rest protects data on storage media but does not address residual data in memory, cache, or buffers during runtime. This control requires clearing or sanitizing shared resources when they are deallocated, which encryption alone does not accomplish. Both encryption and resource clearing are typically needed—encryption protects data on disk, while clearing protects data in memory and other volatile resources.
What should we do if we cannot enable memory clearing due to performance concerns?
Performance impact from memory clearing is typically minimal on modern systems. If performance concerns exist, conduct testing to quantify the actual impact. If clearing cannot be enabled, implement compensatory controls such as dedicated systems for CUI processing, enhanced encryption, or reduced resource sharing. Document the risk acceptance and compensatory controls in a POA&M, and work toward enabling clearing as hardware or software is upgraded.
How ConformatIQ Helps With CMMC Readiness
ConformatIQ is an AI-assisted CMMC readiness platform designed to help organizations prepare for assessments more efficiently. The platform supports document generation such as SSPs and POA&Ms, guided readiness workflows, centralized evidence tracking, and interview preparation for assessments.
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Request Full GuidanceInformation sourced from NIST SP 800-171 Rev. 2. See full disclaimer.