Just run in console (our server used sendmail)
# grep 'authid=' /var/log/maillog
copy output, paste it into Exel and sort by user name. User with many enters from strange relay is the spammer.
Mar 16 12:54:03 YOUR.HOST sm-mta[69153]: AUTH=server, relay=mm-131-204-121-178.dynamic.pppoe.mgts.by [178.121.204.131] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:43:16 YOUR.HOST sm-mta[70233]: AUTH=server, relay=195-58-254-11.skif.net [195.58.254.11] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 11:24:11 YOUR.HOST sm-mta[68458]: AUTH=server, relay=mx-ll-223.207.245-236.dynamic.3bb.co.th [223.207.245.236] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:18:39 YOUR.HOST sm-mta[68892]: AUTH=server, relay=46-211-65-82-krr.broadband.kyivstar.net [46.211.65.82] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:52:03 YOUR.HOST sm-mta[70302]: AUTH=server, relay=mx-ll-49.49.40-121.dynamic.3bb.co.th [49.49.40.121] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:07:41 YOUR.HOST sm-mta[69296]: AUTH=server, relay=5-105-252-183.mytrinity.com.ua [5.105.252.183] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:39:39 YOUR.HOST sm-mta[69728]: AUTH=server, relay=host-82-201-245-70.static.link.com.eg [82.201.245.70] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:04:54 YOUR.HOST sm-mta[68782]: AUTH=server, relay=85.104.109.79.static.ttnet.com.tr [85.104.109.79] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:04:31 YOUR.HOST sm-mta[68781]: AUTH=server, relay=110.178.151.89.chtts.ru [89.151.178.110] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:25:47 YOUR.HOST sm-mta[68954]: AUTH=server, relay=node-hsh.pool-1-10.dynamic.totbb.net [1.10.218.17], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:02:05 YOUR.HOST sm-mta[68767]: AUTH=server, relay=node-idk.pool-1-4.dynamic.totbb.net [1.4.221.8], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:23:55 YOUR.HOST sm-mta[69509]: AUTH=server, relay=ppp-110-168-12-21.revip5.asianet.co.th [110.168.12.21], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:39:44 YOUR.HOST sm-mta[69055]: AUTH=server, relay=server.211.199.itcsa.net [190.15.211.199], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:28:02 YOUR.HOST sm-mta[68979]: AUTH=server, relay=host-219-68-45-219.dynamic.kbtelecom.net [219.68.45.219], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:15:31 YOUR.HOST sm-mta[70011]: AUTH=server, relay=220-142-136-56.dynamic.hinet.net [220.142.136.56], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:11:58 YOUR.HOST sm-mta[69352]: AUTH=server, relay=112-31-201-46.pool.ukrtel.net [46.201.31.112], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:20:49 YOUR.HOST sm-mta[68905]: AUTH=server, relay=199-246-124-91.pool.ukrtel.net [91.124.246.199], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 10:45:29 YOUR.HOST sm-mta[68112]: AUTH=server, relay=18-112-132-95.pool.ukrtel.net [95.132.112.18], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:22:14 YOUR.HOST sm-mta[68911]: AUTH=server, relay=[123.23.175.62], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:40:07 YOUR.HOST sm-mta[69056]: AUTH=server, relay=[123.20.141.193], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:47:13 YOUR.HOST sm-mta[69119]: AUTH=server, relay=[196.221.150.192], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:06:14 YOUR.HOST sm-mta[69282]: AUTH=server, relay=[37.214.160.219], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:16:33 YOUR.HOST sm-mta[69393]: AUTH=server, relay=[197.135.117.232], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:19:13 YOUR.HOST sm-mta[69437]: AUTH=server, relay=[213.111.176.59], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:03:18 YOUR.HOST sm-mta[69918]: AUTH=server, relay=[117.55.147.100], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:40:26 YOUR.HOST sm-mta[70193]: AUTH=server, relay=[178.120.129.200], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:40:33 YOUR.HOST sm-mta[70194]: AUTH=server, relay=[93.118.92.82], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 15:00:55 YOUR.HOST sm-mta[70424]: AUTH=server, relay=[180.92.5.218], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
# grep 'authid=' /var/log/maillog
copy output, paste it into Exel and sort by user name. User with many enters from strange relay is the spammer.
Mar 16 12:54:03 YOUR.HOST sm-mta[69153]: AUTH=server, relay=mm-131-204-121-178.dynamic.pppoe.mgts.by [178.121.204.131] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:43:16 YOUR.HOST sm-mta[70233]: AUTH=server, relay=195-58-254-11.skif.net [195.58.254.11] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 11:24:11 YOUR.HOST sm-mta[68458]: AUTH=server, relay=mx-ll-223.207.245-236.dynamic.3bb.co.th [223.207.245.236] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:18:39 YOUR.HOST sm-mta[68892]: AUTH=server, relay=46-211-65-82-krr.broadband.kyivstar.net [46.211.65.82] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:52:03 YOUR.HOST sm-mta[70302]: AUTH=server, relay=mx-ll-49.49.40-121.dynamic.3bb.co.th [49.49.40.121] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:07:41 YOUR.HOST sm-mta[69296]: AUTH=server, relay=5-105-252-183.mytrinity.com.ua [5.105.252.183] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:39:39 YOUR.HOST sm-mta[69728]: AUTH=server, relay=host-82-201-245-70.static.link.com.eg [82.201.245.70] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:04:54 YOUR.HOST sm-mta[68782]: AUTH=server, relay=85.104.109.79.static.ttnet.com.tr [85.104.109.79] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:04:31 YOUR.HOST sm-mta[68781]: AUTH=server, relay=110.178.151.89.chtts.ru [89.151.178.110] authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:25:47 YOUR.HOST sm-mta[68954]: AUTH=server, relay=node-hsh.pool-1-10.dynamic.totbb.net [1.10.218.17], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:02:05 YOUR.HOST sm-mta[68767]: AUTH=server, relay=node-idk.pool-1-4.dynamic.totbb.net [1.4.221.8], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:23:55 YOUR.HOST sm-mta[69509]: AUTH=server, relay=ppp-110-168-12-21.revip5.asianet.co.th [110.168.12.21], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:39:44 YOUR.HOST sm-mta[69055]: AUTH=server, relay=server.211.199.itcsa.net [190.15.211.199], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:28:02 YOUR.HOST sm-mta[68979]: AUTH=server, relay=host-219-68-45-219.dynamic.kbtelecom.net [219.68.45.219], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:15:31 YOUR.HOST sm-mta[70011]: AUTH=server, relay=220-142-136-56.dynamic.hinet.net [220.142.136.56], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:11:58 YOUR.HOST sm-mta[69352]: AUTH=server, relay=112-31-201-46.pool.ukrtel.net [46.201.31.112], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:20:49 YOUR.HOST sm-mta[68905]: AUTH=server, relay=199-246-124-91.pool.ukrtel.net [91.124.246.199], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 10:45:29 YOUR.HOST sm-mta[68112]: AUTH=server, relay=18-112-132-95.pool.ukrtel.net [95.132.112.18], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:22:14 YOUR.HOST sm-mta[68911]: AUTH=server, relay=[123.23.175.62], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:40:07 YOUR.HOST sm-mta[69056]: AUTH=server, relay=[123.20.141.193], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 12:47:13 YOUR.HOST sm-mta[69119]: AUTH=server, relay=[196.221.150.192], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:06:14 YOUR.HOST sm-mta[69282]: AUTH=server, relay=[37.214.160.219], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:16:33 YOUR.HOST sm-mta[69393]: AUTH=server, relay=[197.135.117.232], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 13:19:13 YOUR.HOST sm-mta[69437]: AUTH=server, relay=[213.111.176.59], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:03:18 YOUR.HOST sm-mta[69918]: AUTH=server, relay=[117.55.147.100], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:40:26 YOUR.HOST sm-mta[70193]: AUTH=server, relay=[178.120.129.200], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 14:40:33 YOUR.HOST sm-mta[70194]: AUTH=server, relay=[93.118.92.82], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0
Mar 16 15:00:55 YOUR.HOST sm-mta[70424]: AUTH=server, relay=[180.92.5.218], authid= COMPROMISED_USER@YOUR.HOST, mech=PLAIN, bits=0

