pam_tally has several limitations, which are solved with pam_tally2. For this reason pam_tally is deprecated and will be removed in a future release.
pam_tally comes in two parts: pam_tally.so and pam_tally. The former is the PAM module and the latter, a stand-alone program. pam_tally is an (optional) application which can be used to interrogate and manipulate the counter file. It can display users' counts, set individual counts, or clear all counts. Setting artificially high counts may be useful for blocking users without changing their passwords. For example, one might find it useful to clear all counts every midnight from a cron job. The faillog(8) command can be used instead of pam_tally to to maintain the counter file.
Normally, failed attempts to access root will not cause the root account to become blocked, to prevent denial-of-service: if your users aren't given shell accounts and root may only login via su or at the machine console (not telnet/rsh, etc), this is safe.
The auth and account module types are provided.
Add the following line to /etc/pam.d/login to lock the account after too many failed logins. The number of allowed fails is specified by /var/log/faillog and needs to be set with pam_tally or faillog(8) before.
auth required pam_securetty.so auth required pam_tally.so per_user auth required pam_env.so auth required pam_unix.so auth required pam_nologin.so account required pam_unix.so password required pam_unix.so session required pam_limits.so session required pam_unix.so session required pam_lastlog.so nowtmp session optional pam_mail.so standard
faillog(8), pam.conf(5), pam.d(5), pam(7)
pam_tally was written by Tim Baverstock and Tomas Mraz.