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Caution: DNS Vulnerability

Discussion in 'Plesk 10.x for Windows Issues, Fixes, How-To' started by MaxemilianH, Aug 30, 2012.

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Poll closed Oct 29, 2012.
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  1. MaxemilianH

    MaxemilianH Guest

    0
     
    The DNS implementation seems to have a problem:
    When recursion is enabled for localnets, everybody can query the dns server. This opens the server for DoS attacks, and other vulnerabilities.

    How to test
    use nslookup on a computer which should not be in a local net
    > server <your_server_name_or_ip>
    > <any_domain_which_is_not_on_your_dns>

    If it returns valid DNS data, your server is open for vulnerabilities


    How to fix

    Open a command prompt and navigate to the bin directory of your plesk installation
    > cd %plesk_cli%

    Use the following command to restrict dns recursion to localhost:
    > server_dns -u -recursion localhost


    Re-test if the server stops answering requests which cannot be answered locally (message should be "Query refused."), but ensure the domains hosted on your machine can be resolved.


    To reset this to the default setting:
    > server_dns -u -recursion localnets



    regards

    Maxemilian Hilbrand
    www.isicore.de
     
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