CMMC Practice AC.L2-3.1.21 – Portable Storage Use: Limit use of portable storage devices on external systems.
Links to Publicly Available Resources
This document provides assessment guidance for conducting Cybersecurity Maturity Model Certification (CMMC) assessments for Level 2. This is a sample removable storage policy for the Colorado Department of Education. This article provides an overview of removable media including the risks associated with this technology and how to implement a control policy. McAfee Total Protection to reduce the attack surface The USBGuard software framework provides system protection against intrusive USB devices by implementing basic whitelisting and blacklisting capabilities based on device attributes. This sample policy provided by SANS discusses removable media. This SANS whitepaper discusses a holistic approach to USB port-security. This article provides an overview of the risks associated with removable media for industrial facilities based on a 2018 Honeywell report. This paper focuses on the risks associated with simple media devices and smart media devices. In this edition of the On Call Compliance Solutions Compliance Tip of the Week, we discuss placing limits on the use of organization-controlled portable storage devices in external systems including a complete prohibition of the use of such devices or restrictions on how the devices may be used and under what conditions the devices may be used. Let’s talk about NIST 800-171 Control 3.1.21 -- Limit use of portable storage devices on external systems.
Discussion [NIST SP 800-171 R2]
Limits on the use of organization-controlled portable storage devices in external systems include complete prohibition of the use of such devices or restrictions on how the devices may be used and under what conditions the devices may be used. Note that while “external” typically refers to outside of the organization’s direct supervision and authority that is not always the case. Regarding the protection of CUI across an organization, the organization may have systems that process CUI and others that do not. Among the systems that process CUI there are likely access restrictions for CUI that apply between systems. Therefore, from the perspective of a given system, other systems within the organization may be considered “external” to that system.
Further Discussion
A portable storage device is a system component that can be inserted or attached and easily removed from a system. It is used to store data or information. Examples of portable storage devices include:
- compact/digital video disks (CDs/DVDs);
- Universal Serial Bus (USB) drives;
- external hard disk drives;
- flash memory cards/drives; and
- floppy disks.
This practice can be implemented in two ways:
- identifying the portable storage device usage restrictions, identifying portable storage devices that may be used on external systems, identifying associated external systems on which a portable storage device may be used, and administratively (through the use of a written policy) limiting the usage of the devices to those systems; or
- configuring devices to work only when connected to a system to which the portable storage device can authenticate, limiting the devices’ use on external systems to those that the contractor has the ability to manage.