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  1. #1
    Join Date
    May 2009
    Markham, Canada

    * Test for open DNS resolvers (DNS Amplification Attack)

    This script scans all OpenVZ containers on a node for open DNS resolvers:

    echo "Simple script to scan all OpenVZ containers for open DNS resolvers"
    echo "For web-based testing use"
    for ip in `vzlist -H | awk '{print $4}'`;
        OUT=$(dig +short +tries=1 +time=2 TXT @$ip | grep open-resolver-detected)
        if [ -z "$OUT" ]; then
            echo "$ip is not an open resolver"
            echo "$ip IS an open resolver!"
    Quick wget command (run as root):
    chmod 0700

    Sample output:
    Simple script to scan all OpenVZ containers for open DNS resolvers
    For web-based testing use is not an open resolver IS an open resolver! is not an open resolver is not an open resolver

    Manually test an IP address:
    dig +short TXT @
    #Replace with the IP address or domain name of the DNS server you are testing.
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  2. #2
    Thanks for this script.. Its using for me

  3. #3
    Join Date
    Dec 2011
    Very useful for hosting providers. They should all have this running as a cron with mail alerts, so it scans the containers once a week or so or maybe automatically e-mails the clients if they run an open resolver. This is very important in my opinion and most hosters don't care about it. So thanks for sharing!
    Inbound Marketing & real SEO for web hosting providers
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