By limiting the number of failed access 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.
The pam_tally2.so module maintains a count of attempted accesses. This includes user name entry into a logon field as well as password entry. With counting access attempts, it is possible to lock an account without presenting a password into the password field. This should be taken into consideration as it poses as an avenue for denial of service.
Verify the SUSE operating system locks a user account after three consecutive failed access attempts until the locked account is released by an administrator.
Check that the system locks a user account after three consecutive failed login attempts using the following command:
If no line is returned or the line is commented out, this is a finding. If the line is missing "onerr=fail", this is a finding. If the line has "deny" set to a value other than 1, 2, or 3, this is a finding.
Check that the system resets the failed login attempts counter after a successful login using the following command:
Add or modify the following line in the /etc/pam.d/common-account file: account required pam_tally2.so
Note: Manual changes to the listed files may be overwritten by the "pam-config" program. The "pam-config" program should not be used to update the configurations listed in this requirement.