Snort mailing list archives
Re: detection and preprocessor plugins
From: Martin Roesch <roesch () sourcefire com>
Date: Mon, 28 Jan 2002 22:01:31 -0500
On 1/28/02 3:24 PM, "Steve Halligan" <agent33 () geeksquad com> wrote:
I wan't to write a plugin to detect the presence of something in the data portian of a packet. This "something" is too complex and random for a signature, so it needs to be done via a plugin. However, my detection could be completely thwarted be simply fragging the packet. My questions are: 1) Should this be a detection plugin or a preprocessor?
It should be a detection plugin, the frag2 preprocessor will take care of the heavy lifting of defragging packets and presenting them to you in their "correct" format.
2) Is there anyplace that I would have access to the packet that has been reassembled by the defrag prprocessor?
Yes, the frag2 preprocessor hands the defragmented packet to the detection engine in real-time once all the pieces have arrived.
3) If one have multiple preprocessors, what determines the order they run in? Can the defrag run first, then others, allowing them to see the packet in its defragged form?
The order is determined by the way that they're loaded in the snort.conf file. The default order has spp_frag2 loaded first.
4) spp_bo (the back orifice preprocessor) is a preprocessor. If #3 above is not possible, can it be thwarted by running the packets through a fragrouter?
Yes, but most people scanning for BO these days are yahoos... :) -Marty -- Martin Roesch - Founder/CEO Sourcefire Inc. - (410) 552-6999 Sourcefire: Professional Snort Sensor and Management Console appliances roesch () sourcefire com - http://www.sourcefire.com Snort: Open Source Network IDS - http://www.snort.org _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
Current thread:
- detection and preprocessor plugins Steve Halligan (Jan 28)
- Re: detection and preprocessor plugins Martin Roesch (Jan 28)
- <Possible follow-ups>
- RE: detection and preprocessor plugins Steve Halligan (Jan 29)
- RE: detection and preprocessor plugins Steve Halligan (Jan 29)
- Re: detection and preprocessor plugins Martin Roesch (Jan 29)