Snort mailing list archives

Re: Re: I don't get any alerts when reading from file.


From: <dimopoulos () mhl tuc gr>
Date: Tue, 3 Aug 2004 12:27:11 +0300 (EEST)

First of all, thanks for your time!
 Now, here is the entire process I use. I have written a small program in
 C++ that reads all the .rules files that have a 'content' field and
 generates fake IP packets that match those rules. The packets contain all
 the necessary header data (IP and TCP/UDP) to match the rule along with
 the necessary payload (random but with content that matches that of the
 rule). I write these packets in hexdump format and then use the tool
 'text2pcap' of Ethereal to convert it from hexdump to tcpdump
 format,using teh command line "text2pcap -q -l 12 <source>
 <destination>", and after that I take the newly generated file and feed
 it to snort. Using the -vd switches I can see that the IP addresses,
 ports and payload are ok (i.e. should match) yet I get nothing. And the
 fake samples I use are large enough (250000 packets) that at least some
 should have triggered.

How did you create the tcpdump file?  What was the command line you
used with tcpdump?

Can you try running Snort like this:

snort -c snort.conf -A console -b -r test.txt

What makes you think that every packet should be generating an alert?
Which SID do you expect to be firing?

You might want to start with a simpler test to just detect the specific
 alert that you're looking for.  You could even write a custom rule for
 it...

     -Marty



--
Martin Roesch - Founder/CTO, Sourcefire Inc. - (410)290-1616
Sourcefire: Intelligent Security Monitoring
roesch () sourcefire com - http://www.sourcefire.com
Snort: Open Source Network IDS - http://www.snort.org





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