NIST 800-53 REV 5 • ACCESS CONTROL
AC-7 — Unsuccessful Logon Attempts
Enforce a limit of {{ insert: param, ac-07_odp.01 }} consecutive invalid logon attempts by a user during a {{ insert: param, ac-07_odp.02 }} ; and Automatically {{ insert: param, ac-07_odp.03 }} when the maximum number of unsuccessful attempts is exceeded.
Supplemental Guidance
The need to limit unsuccessful logon attempts and take subsequent action when the maximum number of attempts is exceeded applies regardless of whether the logon occurs via a local or network connection. Due to the potential for denial of service, automatic lockouts initiated by systems are usually temporary and automatically release after a predetermined, organization-defined time period. If a delay algorithm is selected, organizations may employ different algorithms for different components of the system based on the capabilities of those components. Responses to unsuccessful logon attempts may be implemented at the operating system and the application levels. Organization-defined actions that may be taken when the number of allowed consecutive invalid logon attempts is exceeded include prompting the user to answer a secret question in addition to the username and password, invoking a lockdown mode with limited user capabilities (instead of full lockout), allowing users to only logon from specified Internet Protocol (IP) addresses, requiring a CAPTCHA to prevent automated attacks, or applying user profiles such as location, time of day, IP address, device, or Media Access Control (MAC) address. If automatic system lockout or execution of a delay algorithm is not implemented in support of the availability objective, organizations consider a combination of other actions to help prevent brute force attacks. In addition to the above, organizations can prompt users to respond to a secret question before the number of allowed unsuccessful logon attempts is exceeded. Automatically unlocking an account after a specified period of time is generally not permitted. However, exceptions may be required based on operational mission or need.
Practitioner Notes
After a certain number of failed login attempts, the system should lock the account or take some other action. This prevents brute-force password attacks by slowing attackers down.
Example 1: Configure the Account Lockout Policy via GPO at Computer Configuration → Policies → Windows Settings → Security Settings → Account Policies → Account Lockout Policy. Set Account lockout threshold to 5 attempts, Account lockout duration to 30 minutes, and Reset account lockout counter after to 30 minutes.
Example 2: In Azure AD, enable Smart Lockout under Azure AD → Security → Authentication Methods → Password Protection. Set the lockout threshold to 10 and the lockout duration to 60 seconds. Smart Lockout learns your users' sign-in patterns and avoids locking out legitimate users while still blocking attacks.