Monitor NXDOMAIN Unknown Answers (Failures)


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L0 Member

Monitor NXDOMAIN Unknown Answers (Failures)

Does anyone know if it is possible to monitor for NXDOMAIN Unknown Answers (Failures) with PanOS 5.0 ?

Would it be a custom signature/application that needs to be created?

Tags (1)
L6 Presenter

I did not hear about any function doing that.

if Nxdomain answers has a common criteria maybe....

L6 Presenter

According to the manual "DNS" is currently not available (in PANOS 5.0) as decoder for custom signatures.

If it were you would be able to create a custom signature that brings you an alert (a log entry) each time a NXDOMAIN answer is seen.

Without the decoder you can still create a custom signature based on the hex-values but then this string must be 7 chars (or something like that) and you will most likely get a bunch of false positives because this string is matched through the whole session and not just in a specific "field".

L4 Transporter

Hello Bengbrewer,

You can create a Custom Vulnerability Signature to look for the HEX values in a DNS Response header part of a packet that has the No Such Name flag (NXDOMAIN).  Below is my custom signature to do just that.

<vulnerability-threat version="6.0.0">

  <entry name="41000">



        <entry name="NXDOMAIN">


            <entry name="And Condition 1">


                <entry name="Or Condition 1">




























Hope it helps.

Kind regards,


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