Snort mailing list archives
Re: Reassembled packets from Frag3 and Stream5
From: "Matt Olney" <molney () sourcefire com>
Date: Tue, 14 Oct 2008 09:00:05 -0400
The reassembled packets are identical to the combined payloads of the packets that are reassembled. Snort reinjects the reassembled packets (pseudopackets) at the decoder level and detection is run against the reassembled packets. While this does indeed add load to the system, this cost is entirely acceptable given the decrease in trivial evasion possibilies and is more than offset by the by performance increase that is gained by handling flows with an understanding of the stream state. Matt On Tue, Oct 14, 2008 at 4:42 AM, Rayne <hjazz6 () ymail com> wrote:
Hi all, I know that Frag3 reassembles IP fragments, and Stream5 reassembles TCP fragments. So are the reassembled packets identical, i.e. in terms of payload? And wouldn't this increase the volume of traffic passed into the detection engine and cause it to run slower, since there are now more packets to check against the rules? Thank you. Regards, Rayne ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ 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<https://lists.sourceforge.net/lists/listinfo/snort-usersSnort-users>list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
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Current thread:
- Reassembled packets from Frag3 and Stream5 Rayne (Oct 14)
- Re: Reassembled packets from Frag3 and Stream5 Matt Olney (Oct 14)
- <Possible follow-ups>
- Re: Reassembled packets from Frag3 and Stream5 Wu Wei Dong (Oct 14)
- Re: Reassembled packets from Frag3 and Stream5 Matt Olney (Oct 15)
- Re: Reassembled packets from Frag3 and Stream5 Rayne (Oct 15)
- Re: Reassembled packets from Frag3 and Stream5 Matt Olney (Oct 15)