root@mainhost [~]# cat /var/log/secure | grep 'sshd.*Invalid'
May 17 21:07:28 mainhost sshd[30115]: Invalid user admin from 193.104.41.87
May 17 21:07:31 mainhost sshd[30119]: Invalid user admin from 193.104.41.87
May 17 21:07:34 mainhost sshd[30125]: Invalid user admin from 193.104.41.87
May 17 23:55:26 mainhost sshd[26499]: Invalid user teamspeak from 5.196.95.124
May 17 23:55:28 mainhost sshd[26504]: Invalid user teamspeak from 5.196.95.124
May 17 23:55:31 mainhost sshd[26508]: Invalid user teamspeak from 5.196.95.124
May 19 00:49:11 mainhost sshd[25972]: Invalid user \357\273\277root from 5.196.67.137
May 20 06:23:17 mainhost sshd[13178]: Invalid user \357\273\277root from 218.28.152.162
May 20 09:15:37 mainhost sshd[12265]: Invalid user mengli2 from 187.174.116.253
May 20 10:41:50 mainhost sshd[27320]: Invalid user admin from 203.217.175.22
May 20 11:29:58 mainhost sshd[3067]: Invalid user technicom from 31.184.194.115
May 20 19:18:03 mainhost sshd[24157]: Invalid user scan from 31.184.194.115
May 20 23:15:18 mainhost sshd[31082]: Invalid user admin from 31.184.194.115
May 21 03:11:35 mainhost sshd[5063]: Invalid user admin from 31.184.194.115
May 21 04:54:32 mainhost sshd[22205]: Invalid user admin from 91.194.254.145
May 21 04:54:38 mainhost sshd[22213]: Invalid user admin from 91.194.254.144
May 21 04:54:41 mainhost sshd[22217]: Invalid user admin from 91.194.254.143
May 21 04:54:44 mainhost sshd[22221]: Invalid user admin from 91.194.254.144
May 21 07:07:35 mainhost sshd[11331]: Invalid user dragon from 31.184.194.115
May 21 11:05:43 mainhost sshd[18805]: Invalid user test from 31.184.194.115
May 21 16:33:27 mainhost sshd[11029]: Invalid user stud from 54.225.140.125
May 21 16:39:11 mainhost sshd[11895]: Invalid user stephanie from 54.225.140.125
May 21 19:00:44 mainhost sshd[3972]: Invalid user support from 31.184.194.115
May 21 23:03:04 mainhost sshd[12910]: Invalid user guest from 31.184.194.115
May 22 02:58:17 mainhost sshd[20004]: Invalid user "null" from 52.8.78.105
May 22 02:58:25 mainhost sshd[20013]: Invalid user ubuntu from 52.8.78.105
May 22 06:55:13 mainhost sshd[26870]: Invalid user admin from 58.108.232.7
May 22 09:55:05 mainhost sshd[24555]: Invalid user test from 58.108.232.7
May 22 11:48:14 mainhost sshd[10597]: Invalid user zhangyan from 83.221.105.73
May 22 11:48:16 mainhost sshd[10602]: Invalid user dff from 83.221.105.73