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Exim dictionary attack to non existant domain on server

Discussion in 'E-mail Discussions' started by sahostking, Aug 26, 2016.

  1. sahostking

    sahostking Well-Known Member

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    Have a massive attack of over 500 connections sometimes from random IP addresses all over in different countries to a particular domain of a client that was with us a year ago and the account is already terminated off server months ago.

    Not sure what to do to stop it?

    - Removed -

    Code:
    2016-08-26 01:39:36 H=(dynamic.vdc.vn) [123.24.93.225]:27531 F=<jkelli@anotherexample.net> rejected RCPT <bac38a10b@domain.co.za>: Please turn on SMTP Authentication in your mail client. (dynamic.vdc.vn) [123.24.93.225]:27531 is not permitted to relay through this server without authentication.
    2016-08-26 01:39:37 H=([181.66.107.188]) [190.42.36.32]:41405 F=<nicolap@example.co.za> rejected RCPT <pltassh341@domain.co.za>: Please turn on SMTP Authentication in your mail client. ([181.66.107.188]) [190.42.36.32]:41405 is not permitted to relay through this server without authentication.
    
     
    #1 sahostking, Aug 26, 2016
    Last edited by a moderator: Aug 26, 2016
  2. ruzbehraja

    ruzbehraja Well-Known Member

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    They may have left their DNS / A Records pointing to your server.

    What you could do, in the cPanel DNS is , add that domain and set all A records for it to "127.0.0.1".

    When the attackers try to resolve that domain name, it will lead them to their own machine's loopback :)
     
  3. sahostking

    sahostking Well-Known Member

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    Checked and see no dns. But will create an account for it and then do just that.
     
  4. mtindor

    mtindor Well-Known Member

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    I don't even think you have to add a new account for it. Within WHM, just create a new zone for that domain. Better to have just a zone file exist rather than a whole hosting account. Just my two thoughts.

    Mike
     
  5. ruzbehraja

    ruzbehraja Well-Known Member

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    I agree on this.
     
  6. cPanelMichael

    cPanelMichael Forums Analyst
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    Hello,

    I agree, this seems like the most plausible reason this is happening. You may also want to consider reaching out to the contact address for that domain name in it's WHOIS lookup to let them know of the situation.

    Thank you.
     
  7. sahostking

    sahostking Well-Known Member

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    The domain was somewhere else - It seems they are attacking the hostname or IP of the server somehow and doing a dictionary attack against it for that domain. Seems to have stopped but still get a little connections now and again.
     
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