log file entries

For about a year now, we are seeing an ever increasing auth failure in our log file and wonder if you could give us some hints on how to track this down to an IP address or somehow block it.

Dec 2 06:52:14 gto saslauthd[1311]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 06:52:18 gto saslauthd[1310]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 06:52:20 gto saslauthd[1310]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 06:52:20 gto saslauthd[1310]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 06:53:13 gto saslauthd[1312]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 06:53:15 gto saslauthd[1312]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 06:53:15 gto saslauthd[1312]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 06:59:45 gto saslauthd[1312]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 06:59:47 gto saslauthd[1312]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 06:59:47 gto saslauthd[1312]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 06:59:48 gto saslauthd[1315]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 06:59:50 gto saslauthd[1315]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 06:59:50 gto saslauthd[1315]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:12:06 gto saslauthd[1314]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:12:08 gto saslauthd[1314]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 07:12:08 gto saslauthd[1314]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:12:11 gto saslauthd[1315]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:12:13 gto saslauthd[1315]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 07:12:13 gto saslauthd[1315]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:13:03 gto saslauthd[1314]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:13:05 gto saslauthd[1314]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 07:13:05 gto saslauthd[1314]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:14:45 gto saslauthd[1315]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:14:47 gto saslauthd[1315]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 07:14:47 gto saslauthd[1315]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:14:48 gto saslauthd[1314]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:14:50 gto saslauthd[1314]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 07:14:50 gto saslauthd[1314]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:17:22 gto saslauthd[1315]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:17:24 gto saslauthd[1315]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure Dec 2 07:17:24 gto saslauthd[1315]: do_auth : auth failure: [user=bob] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error] Dec 2 07:17:29 gto saslauthd[1314]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= Dec 2 07:17:31 gto saslauthd[1314]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure

Thanks for any advice you can give. Jeff