On 15-09-29 03:05 PM, Harrison Johnson wrote:
Generally speaking you could use a multi-line regex to look for the sequence then ban the offending IP or you could use a single line regex to ban all users for a short amount of time on disconnect and use the recidive jail to ban a large number of disconnects.



OK, Here is what I did to stop this attack.

I created a new filter:
[root@szeta fail2ban]# cat filter.d/postfix-auth.conf
[INCLUDES]

before = common.conf

[Definition]

_daemon = postfix/(submission/)?smtp(d|s)

failregex = ^%(__prefix_line)slost connection after AUTH from (.*)\[<HOST>\]

ignoreregex =

[Init]

journalmatch = _SYSTEMD_UNIT=postfix.service



Then enables the jail in jail.local
[postfix-auth]
enabled = true
port     = smtp,465,submission,imap3,imaps,pop3,pop3s
logpath  = %(syslog_mail)s
action = %(action_mwl)s
bantime  = 604800
findtime  = 600
maxretry = 5


Restart fail2ban. Then I got the alert mail:

Hi,

The IP 37.187.77.147 has just been banned by Fail2Ban after
1736 attempts against postfix-auth.



Thank you for the help.


Gao


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