[Bro] Correlate DNS request/response with TCP/UDP connections

Jason Trost jason.trost at gmail.com
Thu Oct 10 03:50:21 PDT 2013

Is there a good way to correlate DNS requests/responses with subsequent
TCP/UDP connections using Bro (in realtime)?  With how my tap is configured
I can see the client's DNS request/response and all their traffic.  I want
to be able to combine their DNS request (if there is one) with the
corresponding TCP/UDP following it.  For my use case I need this to be done
in realtime (not later by simply doing a JOIN).  So, I am interested in a
single log entry with DNS request/response AND connection info.

It seems like this should be possible by basically doing the following:

    dns_response.dst_ip == conn.src_ip AND
    conn.dst_ip == dns_response.answer_ip AND
    (conn.timestamp - dns_response.timestamp) < THRESHOLD

Has anyone done this?  Any guidance would be greatly appreciated.


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