pam_warn.so
pam_warn is a PAM module that logs the service, terminal, user, remote user and remote host to syslog(3) . The items are not probed for, but instead obtained from the standard PAM items. The module always returns PAM_IGNORE, indicating that it does not want to affect the authentication process.
#%PAM-1.0
#
# If we don't have config entries for a service, the
# OTHER entries are used. To be secure, warn and deny
# access to everything.
other auth required pam_warn.so
other auth required pam_deny.so
other account required pam_warn.so
other account required pam_deny.so
other password required pam_warn.so
other password required pam_deny.so
other session required pam_warn.so
other session required pam_deny.so