Eu tenho um servidor freenas há quase um ano e esta é a terceira vez no mês em que recebo um email de segurança com todas as tentativas de login ssh que não são de mim ou de alguém que conheço.
freenas.local login failures:
May 3 00:00:38 freenas sshd[40708]: Invalid user postgres from 222.138.139.252
May 3 00:00:38 freenas sshd[40708]: input_userauth_request: invalid user postgres [preauth]
May 3 00:00:38 freenas sshd[40708]: Failed password for invalid user postgres from 222.138.139.252 port 9224 ssh2
May 3 00:13:20 freenas sshd[40981]: Invalid user zabbix from 154.66.147.4
May 3 00:13:20 freenas sshd[40981]: input_userauth_request: invalid user zabbix [preauth]
May 3 00:13:20 freenas sshd[40981]: Failed password for invalid user zabbix from 154.66.147.4 port 58938 ssh2
May 3 00:21:41 freenas sshd[41198]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 00:43:53 freenas sshd[41773]: Invalid user admin from 222.138.139.252
May 3 00:43:53 freenas sshd[41773]: input_userauth_request: invalid user admin [preauth]
May 3 00:43:53 freenas sshd[41773]: Failed password for invalid user admin from 222.138.139.252 port 9224 ssh2
May 3 00:43:54 freenas sshd[41773]: Failed password for invalid user admin from 222.138.139.252 port 9224 ssh2
May 3 01:05:44 freenas sshd[42330]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 01:26:47 freenas sshd[42820]: Invalid user guest from 222.138.139.252
May 3 01:26:47 freenas sshd[42820]: input_userauth_request: invalid user guest [preauth]
May 3 01:26:47 freenas sshd[42820]: Failed password for invalid user guest from 222.138.139.252 port 9224 ssh2
May 3 01:47:48 freenas sshd[43330]: Invalid user test from 222.138.139.252
May 3 01:47:48 freenas sshd[43330]: input_userauth_request: invalid user test [preauth]
May 3 01:47:48 freenas sshd[43330]: Failed password for invalid user test from 222.138.139.252 port 9224 ssh2
May 3 01:53:07 freenas sshd[43460]: Invalid user guest from 31.184.198.95
May 3 01:53:07 freenas sshd[43460]: input_userauth_request: invalid user guest [preauth]
May 3 01:53:07 freenas sshd[43460]: Failed password for invalid user guest from 31.184.198.95 port 51000 ssh2
May 3 01:54:03 freenas sshd[43497]: Invalid user guest from 31.184.198.95
May 3 01:54:03 freenas sshd[43497]: input_userauth_request: invalid user guest [preauth]
May 3 01:54:03 freenas sshd[43497]: Failed password for invalid user guest from 31.184.198.95 port 41555 ssh2
May 3 01:54:04 freenas sshd[43499]: Invalid user guest from 31.184.198.95
May 3 01:54:04 freenas sshd[43499]: input_userauth_request: invalid user guest [preauth]
May 3 01:54:04 freenas sshd[43499]: Failed password for invalid user guest from 31.184.198.95 port 41915 ssh2
May 3 02:08:41 freenas sshd[43880]: Invalid user info from 222.138.139.252
May 3 02:08:41 freenas sshd[43880]: input_userauth_request: invalid user info [preauth]
May 3 02:08:41 freenas sshd[43880]: Failed password for invalid user info from 222.138.139.252 port 9224 ssh2
May 3 02:12:58 freenas sshd[43989]: Invalid user admin from 31.184.198.95
May 3 02:12:58 freenas sshd[43989]: input_userauth_request: invalid user admin [preauth]
May 3 02:12:58 freenas sshd[43989]: Failed password for invalid user admin from 31.184.198.95 port 50234 ssh2
May 3 02:30:36 freenas sshd[44406]: Invalid user ubnt from 222.138.139.252
May 3 02:30:36 freenas sshd[44406]: input_userauth_request: invalid user ubnt [preauth]
May 3 02:30:36 freenas sshd[44406]: Failed password for invalid user ubnt from 222.138.139.252 port 9224 ssh2
May 3 02:30:43 freenas sshd[44408]: Invalid user admin from 31.184.198.95
May 3 02:30:43 freenas sshd[44408]: input_userauth_request: invalid user admin [preauth]
May 3 02:30:43 freenas sshd[44408]: Failed password for invalid user admin from 31.184.198.95 port 38066 ssh2
May 3 02:53:19 freenas sshd[44953]: Invalid user PlcmSpIp from 222.138.139.252
May 3 02:53:19 freenas sshd[44953]: input_userauth_request: invalid user PlcmSpIp [preauth]
May 3 02:53:19 freenas sshd[44953]: Failed password for invalid user PlcmSpIp from 222.138.139.252 port 9224 ssh2
May 3 03:18:35 freenas sshd[46224]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 03:18:36 freenas sshd[46224]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 03:18:36 freenas sshd[46224]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 03:23:59 freenas sshd[46343]: Failed password for root from 220.124.151.130 port 53283 ssh2
May 3 03:24:02 freenas sshd[46345]: Failed password for root from 220.124.151.130 port 54390 ssh2
May 3 03:24:04 freenas sshd[46347]: Failed password for root from 220.124.151.130 port 55220 ssh2
May 3 03:24:07 freenas sshd[46349]: Invalid user syslog from 220.124.151.130
May 3 03:24:07 freenas sshd[46349]: input_userauth_request: invalid user syslog [preauth]
May 3 03:24:07 freenas sshd[46349]: Failed password for invalid user syslog from 220.124.151.130 port 56104 ssh2
May 3 03:24:09 freenas sshd[46374]: Invalid user syslog from 220.124.151.130
May 3 03:24:09 freenas sshd[46374]: input_userauth_request: invalid user syslog [preauth]
May 3 03:24:09 freenas sshd[46374]: Failed password for invalid user syslog from 220.124.151.130 port 57054 ssh2
May 3 03:42:50 freenas sshd[46890]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 03:42:50 freenas sshd[46890]: Failed password for root from 222.138.139.252 port 9224 ssh2
May 3 04:04:26 freenas sshd[47508]: Invalid user ftpuser from 222.138.139.252
May 3 04:04:26 freenas sshd[47508]: input_userauth_request: invalid user ftpuser [preauth]
May 3 04:04:26 freenas sshd[47508]: Failed password for invalid user ftpuser from 222.138.139.252 port 9224 ssh2
May 3 04:28:17 freenas sshd[48044]: Invalid user support from 222.138.139.252
May 3 04:28:17 freenas sshd[48044]: input_userauth_request: invalid user support [preauth]
May 3 04:28:17 freenas sshd[48044]: Failed password for invalid user support from 222.138.139.252 port 9224 ssh2
May 3 04:51:52 freenas sshd[48631]: Invalid user debian from 222.138.139.252
May 3 04:51:52 freenas sshd[48631]: input_userauth_request: invalid user debian [preauth]
May 3 04:51:52 freenas sshd[48631]: Failed password for invalid user debian from 222.138.139.252 port 9224 ssh2
May 3 05:14:51 freenas sshd[49227]: Invalid user ubuntu from 222.138.139.252
May 3 05:14:51 freenas sshd[49227]: input_userauth_request: invalid user ubuntu [preauth]
May 3 05:14:51 freenas sshd[49227]: Failed password for invalid user ubuntu from 222.138.139.252 port 9224 ssh2
May 3 05:14:52 freenas sshd[49227]: Failed password for invalid user ubuntu from 222.138.139.252 port 9224 ssh2
May 3 06:26:16 freenas sshd[50976]: Invalid user ubnt from 146.0.79.253
May 3 06:26:16 freenas sshd[50976]: input_userauth_request: invalid user ubnt [preauth]
May 3 06:26:16 freenas sshd[50976]: Failed password for invalid user ubnt from 146.0.79.253 port 41046 ssh2
May 3 12:45:27 freenas sshd[17582]: Failed password for root from 176.122.49.3 port 51726 ssh2
May 3 12:45:27 freenas sshd[17584]: Invalid user naseej from 176.122.49.3
May 3 12:45:27 freenas sshd[17584]: input_userauth_request: invalid user naseej [preauth]
May 3 12:45:27 freenas sshd[17584]: Failed password for invalid user naseej from 176.122.49.3 port 52087 ssh2
May 3 12:45:29 freenas sshd[17586]: Failed password for root from 176.122.49.3 port 52432 ssh2
May 3 12:45:33 freenas sshd[17588]: Failed password for root from 176.122.49.3 port 53080 ssh2
May 3 12:45:37 freenas sshd[17590]: Invalid user syslog from 176.122.49.3
May 3 12:45:37 freenas sshd[17590]: input_userauth_request: invalid user syslog [preauth]
May 3 12:45:37 freenas sshd[17590]: Failed password for invalid user syslog from 176.122.49.3 port 54596 ssh2
May 3 12:45:38 freenas sshd[17592]: Invalid user shadmin from 176.122.49.3
May 3 12:45:38 freenas sshd[17592]: input_userauth_request: invalid user shadmin [preauth]
May 3 12:45:38 freenas sshd[17592]: Failed password for invalid user shadmin from 176.122.49.3 port 56197 ssh2
May 3 12:45:39 freenas sshd[17594]: Invalid user icnanker from 176.122.49.3
May 3 12:45:39 freenas sshd[17594]: input_userauth_request: invalid user icnanker [preauth]
May 3 12:45:39 freenas sshd[17594]: Failed password for invalid user icnanker from 176.122.49.3 port 56891 ssh2
May 3 12:45:40 freenas sshd[17596]: Failed password for root from 176.122.49.3 port 57199 ssh2
May 3 12:45:40 freenas sshd[17598]: Invalid user nano from 176.122.49.3
May 3 12:45:40 freenas sshd[17598]: input_userauth_request: invalid user nano [preauth]
May 3 12:45:40 freenas sshd[17598]: Failed password for invalid user nano from 176.122.49.3 port 57535 ssh2
May 3 12:45:42 freenas sshd[17600]: Failed password for root from 176.122.49.3 port 57814 ssh2
May 3 12:45:46 freenas sshd[17602]: Failed password for root from 176.122.49.3 port 58502 ssh2
May 3 12:45:49 freenas sshd[17604]: Failed password for root from 176.122.49.3 port 59876 ssh2
May 3 12:45:51 freenas sshd[17606]: Invalid user syslog from 176.122.49.3
May 3 12:45:51 freenas sshd[17606]: input_userauth_request: invalid user syslog [preauth]
May 3 12:45:51 freenas sshd[17606]: Failed password for invalid user syslog from 176.122.49.3 port 32837 ssh2
May 3 12:45:53 freenas sshd[17608]: Failed password for root from 176.122.49.3 port 33403 ssh2
-- End of security output --
Então, onde ou como posso ver se alguém que não conheço conseguiu efetuar login no meu servidor e, em caso afirmativo, que medidas devo tomar para atualizar a segurança no meu servidor?