[2/27/24, 11:00 AM EST] CSRC has been experiencing technical issues. If you are unable to access a CSRC page or resource, or get a 503 error, please try reloading the page several times--it may help to wait a few minutes before trying again. We apologize for the inconvenience, and hope to have a solution in place next week.
Denotes either a patch level or a patch set. More specifically, when patches must be applied in order, the patch level is the identifier of the most recently applied patch.
NISTIR 8011 Vol. 4