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<p class=MsoNormal>Hi hoping someone can help me a little with this one.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I have 2 mail servers, the incoming mail server runs dovecot
and the outgoing mail server runs postfix with sasl.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Lately I noticed a lot of spammers are running dictionary attacks
on my incoming server and then using that user/password for sasl on the
outgoing server.<o:p></o:p></p>
<p class=MsoNormal>The weird thing is I never see on the logs the guessed
username/password. I always see the ones they can’t guess.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For example:<o:p></o:p></p>
<p class=MsoNormal>Looking at the logs I see the following dictionary
attack from 94.242.206.37<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: pop3-login: Disconnected:
rip=94.242.206.37, lip=209.213.66.10<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default): client in:
AUTH 1
PLAIN service=POP3
lip=209.213.66.10
rip=94.242.206.37 resp=<hidden><o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(aarhus,94.242.206.37): lookup<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default): client in:
AUTH 1
PLAIN service=POP3
lip=209.213.66.10
rip=94.242.206.37 resp=<hidden><o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(abaft,94.242.206.37): lookup<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(abaft,94.242.206.37): unknown user<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default): client in:
AUTH 1
PLAIN service=POP3
lip=209.213.66.10
rip=94.242.206.37 resp=<hidden><o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(aarhus,94.242.206.37): unknown user<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default): client in:
AUTH 1
PLAIN service=POP3
lip=209.213.66.10
rip=94.242.206.37 resp=<hidden><o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(aaron,94.242.206.37): lookup<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(aaron,94.242.206.37): unknown user<o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default): client in:
AUTH 1
PLAIN service=POP3
lip=209.213.66.10
rip=94.242.206.37 resp=<hidden><o:p></o:p></p>
<p class=MsoNormal>Nov 10 03:04:38 pop dovecot: auth(default):
shadow(ababa,94.242.206.37): lookup<o:p></o:p></p>
<p class=MsoNormal>…………. And so on..<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Then that ip gets banned by fail2ban<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>[root@pop ~]# grep 94.242.206.37 /var/log/fail2ban.log<o:p></o:p></p>
<p class=MsoNormal>2010-11-10 03:04:42,416 fail2ban.actions: WARNING [dovecot]
Ban 94.242.206.37<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>However on my outgoing mail server that ip is already
sending out all sorts of spam with the sasl username of Paramus. <o:p></o:p></p>
<p class=MsoNormal>This username Paramus never shows up on the dovecot
dictionary attack log, as a matter of fact the user Paramus is nowhere to be
found on the dovecot log at all and I have logs going back months. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>/var/log/maillog:Nov 10 02:46:16 mrelay3
postfix/smtpd[27776]: 3B64928015: client=unknown[94.242.206.37],
sasl_method=LOGIN, sasl_username=paramus<o:p></o:p></p>
<p class=MsoNormal>/var/log/maillog:Nov 10 02:47:54 mrelay3
postfix/smtpd[27776]: 247AB28016: client=unknown[94.242.206.37],
sasl_method=LOGIN, sasl_username=paramus<o:p></o:p></p>
<p class=MsoNormal>/var/log/maillog:Nov 10 02:48:00 mrelay3
postfix/smtpd[27785]: 87DE128016: client=unknown[94.242.206.37],
sasl_method=LOGIN, sasl_username=paramus<o:p></o:p></p>
<p class=MsoNormal>/var/log/maillog:Nov 10 02:56:00 mrelay3
postfix/smtpd[27792]: 9728628015: client=unknown[94.242.206.37],
sasl_method=LOGIN, sasl_username=paramus<o:p></o:p></p>
<p class=MsoNormal>/var/log/maillog:Nov 10 03:05:38 mrelay3 postfix/smtpd[27808]:
D529F28015: client=unknown[94.242.206.37], sasl_method=LOGIN,
sasl_username=paramus<o:p></o:p></p>
<p class=MsoNormal>/var/log/maillog:Nov 10 03:06:00 mrelay3
postfix/smtpd[27808]: DDF7C2801B: client=unknown[94.242.206.37],
sasl_method=LOGIN, sasl_username=Paramus<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Does anyone have any idea what could of happened here. I
mean if the user/passwd was already harvested by 94.242.206.37 why
would they bother to start another dict. attack. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’m just not sure how they guess the username/password
as its not on any logs that goes back months and I don’t have a dovecot
fail record for that user on the logs. This is the case all the time for me and
it happens with other ips.<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>Any help would be appreciated.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>paul<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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