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Brute Force and ACL

Discussion in 'General Discussion' started by onaweb, Jun 12, 2006.

  1. onaweb

    onaweb Well-Known Member

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    I thought that with Brute Force and the ACL installed that after 3 errors the IP would be blocked.

    I am receiving e-mail that state that:
    The remote system 61.51.184.151 was found to have exceeded acceptable login failures on dserv.onahosting.com; there was 58 events to the service exim. As such the attacking host has been banned from further accessing this system. For the integrity of your host you should investigate this event as soon as possible.

    Executed ban command:
    /etc/apf/apf -d 61.51.184.151 {bfd.exim}

    These are all e-mail to johnson@domain.com and smith@domain.com, etc. If I have the exim config set to 3, why is that there are 58 events, shouldn't the IP be blocked after 3?

    Thanks,
    Andy
     
  2. neonix

    neonix Well-Known Member

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    APF/BFD will block multiple failures but you cannot set an exact number. You might even see upto 1000 login failure messages before the offending i.p is banned...
     
  3. nickp666

    nickp666 Well-Known Member

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    BFD only runs on a cron job, it is not a daemon and therefore is not aware of the system state, it works by checking the secure log at set intervals, and if the login failures exceed the boundary you set it blocks the address
     
  4. onaweb

    onaweb Well-Known Member

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    Thank you for your replies so far. My understanding was that the ACL filter in Exim (which is set to 3 attempts) would block further transmission after those 3 attempts.

    So if I have the ACL set to 3 attempts, why do I receive message that state that there were over 50 attempts?

    Thanks,
    Andy
     
  5. freedog96150

    freedog96150 Well-Known Member

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    I think what the above explanation was trying to get across is that BFD runs at predetermined times from a cron job and not constantly, like a deamon does.

    So if the cron is set to run BFD every 15 minuets and in that 15 minutes an offending IP attempts to penetrate yoru server 2 times, then that IP will not be blocked and you will get no message. Remember that you set the threshold at 3 attempts. Now lets take that same offending IP, but now he has attempted 50 times in that 15 minutes, then the next time the cron runs, it will notice that the IP has exceeded the 3 attempts and the IP will be banned.

    Again, it is not 3 attempts that will get the IP banned, but IF the offending IP had more than 3 attempts BETWEEN the run times of the cron.

    Hope this helps!
    Brian
     
  6. ramprage

    ramprage Well-Known Member

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