Vulnerability Discussion

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account.

Check

Note: If the system administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

Verify Amazon Linux 2023 locks an account after three unsuccessful logon attempts within a period of 15 minutes with the following command:

$ grep fail_interval /etc/security/faillock.conf
fail_interval = 900

If the "fail_interval" option is not set to "900" or less (but not "0"), the line is commented out, or the line is missing, this is a finding.

Fix

Configure Amazon Linux 2023 to automatically lock an account after three unsuccessful logon attempts in 15-minutes.

First, ensure that the system is configured with authselect, i.e., using sssd profiles:

$ sudo authselect select sssd [--force]

Then, enable the faillock feature:

$ sudo authselect enable-feature with-faillock

Then edit the "/etc/security/faillock.conf" file as follows:

fail_interval = 900