1. During working hours, reasonable steps shall be taken to minimize the risk of access by unauthorized personnel. This would include things like placing cover sheets on CUI documents and allowing unescorted access to areas where CUI (documents and AIS storage media) is processed/handled to only those persons with at least a favorably adjudicated National Agency Check (NAC). 2. After working hours, CUI information (documents and removable media) may be stored in unlocked containers, desks, or cabinets if government or government-contract building security is provided. If such building security is not provided or is deemed inadequate, the information (documents and removable media) must be stored in locked desks, file cabinets, bookcases, locked rooms, etc. In all cases, CUI documents must be placed out of sight during nonworking hours. While not required, recommending implementation of a clean desk policy would be appropriate. 3. Unescorted access to computer rooms or areas containing major items of AIS equipment processing CUI information (servers and network components) must only be granted to persons with at least a favorable NAC. All others must be physically escorted. Access control measures such as reception personnel, guards, keyed locks, cipher locks, or automated access control systems may be used to control access to such areas. TACTICAL ENVIRONMENT: The check is applicable for fixed (established) tactical processing environments where procedural documents (SOPs) should be in place. Not applicable to a field/mobile environment.