Re: Using DNS response fields in an alert msg

["Joel Esler (jesler)" <jesler () cisco com>]

David,

An interesting idea.  We’ve written this down.


On Jan 22, 2015, at 10:02 AM, David Longenecker <david () 7longeneckers com<mailto:david () 7longeneckers com>> wrote:

> A similar problem occurs with the "sinkhole" rules. We push our http
> traffic through content filtering proxies and snort still catches the
> stuff the proxies miss, such as "BLACKLIST Connection to malware
> sinkhole". It would be much more useful if that rule was "BLACKLIST
> Connection to malware sinkhole on %HTTP.Header.Host" because then we
> could use the hostname to compare with the proxy logs to actually
> discover the client IP

I think I've found a partial solution. I found a modified dns preprocessor and plugin that parse the entire DNS packet: 
http://www.geocities.ws/axonpotential/snort/18/index.html

It was intended for header inspection, but in reviewing the source code it appears to also parse the data; with a 
little work I believe I will be able to get at the question and answer data, which leaves me with data in hand but no 
way to get that data into my alert message.

Does the msg field of the alert module expand variables, and if so, what's the context? What variables would be 
available? I haven't seen any examples of a variablized alert message in the rules.



--

Regards,
David Longenecker

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