InformationLocking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems.
SolutionEdit the /etc/pam.d/password-auth and /etc/pam.d/system-auth files and add the following pam_faillock.so lines surrounding a pam_unix.so line modify the pam_unix.so is [success=1 default=bad] as listed in both:
auth required pam_faillock.so preauth audit silent deny=5 unlock_time=900
auth [success=1 default=bad] pam_unix.so
auth [default=die] pam_faillock.so authfail audit deny=5 unlock_time=900
auth sufficient pam_faillock.so authsucc audit deny=5 unlock_time=900