大佬们， ssh 设置密钥登陆， lastb 还能看到异常 IP 尝试访问，是啥原因，谢谢

[root@172.21.139.45 ~]# grep "Password" /etc/ssh/sshd_config
#PermitEmptyPasswords no
PasswordAuthentication no

[root@172.21.139.45 ~]# lastb admin ssh:notty 37.76.137.129 Thu Jun 27 08:27 - 08:27 (00:00)
admin ssh:notty 200.196.45.145 Thu Jun 27 08:27 - 08:27 (00:00)
admin ssh:notty 189.112.49.210 Wed Jun 26 12:04 - 12:04 (00:00)
admin ssh:notty 119.42.81.142 Tue Jun 25 15:40 - 15:40 (00:00)
admin ssh:notty 172.220.1.94 Tue Jun 25 15:40 - 15:40 (00:00)
admin ssh:notty 113.184.184.54 Mon Jun 24 00:58 - 00:58 (00:00)
admin ssh:notty 117.244.91.88 Mon Jun 24 00:58 - 00:58 (00:00)
admin ssh:notty 197.35.198.235 Sun Jun 23 04:37 - 04:37 (00:00)
admin ssh:notty 103.124.146.222 Sun Jun 23 04:37 - 04:37 (00:00)
admin ssh:notty 123.20.233.224 Sat Jun 22 08:01 - 08:01 (00:00)
admin ssh:notty 113.186.135.4 Sat Jun 22 08:01 - 08:01 (00:00)
admin ssh:notty 152.246.169.166 Fri Jun 21 07:38 - 07:38 (00:00)
admin ssh:notty 156.194.228.224 Thu Jun 20 18:01 - 18:01 (00:00)
admin ssh:notty 188.124.211.191 Thu Jun 20 04:24 - 04:24 (00:00)

secure log Jun 25 15:40:24 production sshd[31521]: Invalid user admin from 172.220.1.94 port 48677
Jun 25 15:40:24 production sshd[31521]: input_userauth_request: invalid user admin [preauth]
Jun 25 15:40:28 production sshd[31525]: Invalid user admin from 119.42.81.142 port 35310
Jun 25 15:40:28 production sshd[31525]: input_userauth_request: invalid user admin [preauth]
Jun 25 15:40:29 production sshd[31525]: Connection closed by 119.42.81.142 port 35310 [preauth]
Jun 26 08:32:34 production sshd[16352]: Did not receive identification string from 47.94.39.226 port 35456
Jun 26 12:04:14 production sshd[26726]: Invalid user admin from 189.112.49.210 port 38888
Jun 26 12:04:14 production sshd[26726]: input_userauth_request: invalid user admin [preauth]
Jun 26 12:04:15 production sshd[26726]: Connection closed by 189.112.49.210 port 38888 [preauth]
Jun 26 13:55:57 production sshd[32213]: Did not receive identification string from 47.97.21.76 port 47988
Jun 26 20:37:33 production sshd[19534]: Did not receive identification string from 106.15.76.92 port 52986
Jun 27 00:30:54 production sshd[30959]: Did not receive identification string from 47.100.130.114 port 38736
Jun 27 01:33:21 production sshd[1568]: Connection closed by 27.122.59.100 port 43122 [preauth]
Jun 27 01:33:24 production sshd[1573]: Connection closed by 27.122.59.100 port 33213 [preauth]
Jun 27 05:01:55 production sshd[11880]: Connection closed by 132.68.74.160 port 40820 [preauth]
Jun 27 05:25:23 production sshd[13021]: Did not receive identification string from 119.23.138.247 port 38410
Jun 27 08:27:50 production sshd[21953]: Invalid user admin from 200.196.45.145 port 47259
Jun 27 08:27:50 production sshd[21953]: input_userauth_request: invalid user admin [preauth]
Jun 27 08:27:52 production sshd[21953]: Connection closed by 200.196.45.145 port 47259 [preauth]
Jun 27 08:27:54 production sshd[21960]: Invalid user admin from 37.76.137.129 port 60114
Jun 27 08:27:54 production sshd[21960]: input_userauth_request: invalid user admin [preauth]
Jun 27 08:27:55 production sshd[21960]: Connection closed by 37.76.137.129 port 60114 [preauth]
Jun 27 11:49:50 production sshd[31855]: Did not receive identification string from 118.31.244.58 port 47726

大佬们懂的话，说下访问者具体怎么做到的，谢谢