IA.L2-3.5.5  

Reference: CMMC 2.0

Family: IA

Level Introduced: 2

Title: Identifier Reuse

Practice:
Prevent the reuse of identifiers for a defined period.

CMMC Clarification:
Identifiers uniquely associate a user ID to an individual, group, role or device. Establish guidelines and implement mechanisms to prevent identifiers from being reused for the period of time established by the organization in the policy.

Example
As the IT administrator for your organization you maintain a central directory/domain that holds user accounts and computers within the organization. As part of your job you issue unique usernames (joe@acme.com) for the staff to access resources. When you issue staff computers you also rename the computer to reflect to whom it is assigned (joe-laptop01). Joe has recently left the organization so you must manage the former staff member's account. Incidentally, the replacement is also named Joe. In the directory you do not assign the previous account to the new user. You create an account called joe02. This account is assigned the appropriate permissions for the new user. A new laptop is also provided with the identifier of joe02-laptop01.

Source: CMMC v2.0