The Problem

In the past 30 days, I’ve seen over 140,000 entries from many unique ips, which looks like either DOS or password hacking bots, annoying, especially since all my passwords are at least 12 char, random.

 

Top 10 Values	Count	%
162.17.140.61	8,259	5.844%
212.237.47.114	4,583	3.243%
185.227.108.10	1,560	1.104%
192.154.213.123	1,434	1.015%
110.87.25.235	1,356	0.96%
120.35.102.81	1,356	0.96%
117.69.231.207	1,332	0.942%
183.164.244.109	1,327	0.939%
117.69.230.159	1,297	0.918%
117.69.230.216	1,288	0.911%

 

In /var/log/maillog

Apr 22 07:43:21 webhost postfix/smtpd[12521]: lost connection after AUTH from unknown[114.237.43.12]
Apr 22 07:43:19 webhost postfix/smtpd[12521]: lost connection after AUTH from unknown[114.237.43.12]
Apr 22 07:43:17 webhost postfix/smtpd[12521]: lost connection after AUTH from unknown[114.237.43.12]
Apr 22 07:43:14 webhost postfix/smtpd[12521]: lost connection after AUTH from unknown[114.237.43.12]
Apr 22 07:43:08 webhost postfix/smtpd[12521]: lost connection after AUTH from unknown[114.237.43.12]
Apr 22 07:43:06 webhost postfix/smtpd[12521]: lost connection after AUTH from unknown[114.237.43.12]
Apr 22 07:04:24 webhost postfix/smtpd[29802]: lost connection after HELO from unknown[119.86.182.130]
Apr 22 06:35:16 webhost postfix/smtpd[18488]: lost connection after UNKNOWN from unknown[93.174.93.46]

The Fix

Add to /etc/fail2ban/jail.local:

[postfix-auth]
enabled = true
filter = postfix.auth
action = iptables-multiport[name=postfix, port=”http,https,smtp,submission,pop3,pop3s,imap,imaps,sieve”, protocol=tcp]
# sendmail[name=Postfix, dest=you@mail.com]
logpath = /var/log/maillog
bantime = 21600
maxretry = 3

Create /etc/fail2ban/filter.d/postfix.auth.conf

[Definition]
failregex = lost connection after AUTH from (.*)\[\]
ignoreregex =

Problem Solved!