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