The full cidr is blocked in the firewall. 

  Original Message  
From: Patrick Chemla
Sent: Wednesday, November 16, 2016 2:48 AM
To: postfix-users@postfix.org
Subject: Re: hacker or server problem

Le 16/11/2016 à 12:38, li...@lazygranch.com a écrit :
> On Wed, 16 Nov 2016 02:26:13 -0800
> "li...@lazygranch.com" <li...@lazygranch.com> wrote:
>
>> On Wed, 16 Nov 2016 11:52:14 +0200
>> Patrick Chemla <patrick.che...@perfaction.net> wrote:
>>
>>> Le 16/11/2016 à 11:45, li...@lazygranch.com a écrit :
>>>> Is this a hack or a server problem. IP was listed in abusedb
>>>> about a year ago.
>>>>
>>>> <pattern repeats>
>>>> Nov 16 09:14:36 theranch postfix/smtpd[6094]: connect from
>>>> unknown[87.236.215.11] Nov 16 09:14:36 theranch
>>>> postfix/smtpd[6094]: lost connection after AUTH from
>>>> unknown[87.236.215.11] Nov 16 09:14:36 theranch
> <snip>
> # bzgrep -e 87.236.215.11 maillog | wc -l
> 212
>
> Three lines per hack. Make that 70 attempts. The stats line messes up
> the line count.
> First entry:Nov 16 09:13:45
> Last entry: Nov 16 09:18:00
> 255 seconds
> 16.5 attempts a minute
>
16 Attempts per second, yes this is a hack attempt.

Protect yourself immediatly, even if he will surely need some (hundred 
of) thousands attempts to find a password.

Another problem is that he is taking your bandwith.

Patrick

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