Snort mailing list archives
Re: DOS rules for Nimda
From: Martin Roesch <roesch () sourcefire com>
Date: Thu, 26 Sep 2002 10:27:38 -0400
Is the seq number constant for every connection? If so you could do a simple detection rule looking for the seq + window with the SYN flag set. If you use version 1.9 you can even use the new threshold keyword to only get one event notification for every X alerts.... -Marty On 9/26/02 7:11 AM, "Richard Ellerbrock" <richarde () eskom co za> wrote:
I am trying to help a very large site that is being killed by denial of service due to a large number of MS type workstations infected by Nimda. The standard snort rules are no good as no connection is actually made, just a HUGE SYN flood looking for open Web servers to infect. Traffic looks like this: Each host sends 2x SYN packets exactly the same (same source port, SEQ and WIN size) to a remote host on port 80. Obviously never gets a reply. Within a couple of milliseconds, tries another randon destination. Now my understanding of snort points to the stream4 processor to catch this stuff, but how to configure. The docs are a little unclear to this snort newbie. I do get TTL evasion on stream4, but this does not indicate much. Any help with rules/setup for this would be great. ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ 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
-- Martin Roesch - Founder/CTO Sourcefire Inc. - (410) 290-1616 Sourcefire: Professional Snort Sensor and Management Console appliances roesch () sourcefire com - http://www.sourcefire.com Snort: Open Source Network IDS - http://www.snort.org ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ 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:
- DOS rules for Nimda Richard Ellerbrock (Sep 26)
- Re: DOS rules for Nimda Chris Green (Sep 26)
- Re: DOS rules for Nimda Martin Roesch (Sep 26)
- <Possible follow-ups>
- RE: DOS rules for Nimda McCammon, Keith (Sep 26)
- RE: DOS rules for Nimda Tudor Panaitescu (Sep 26)
- RE: DOS rules for Nimda Richard Ellerbrock (Sep 26)
- Re: DOS rules for Nimda Richard Ellerbrock (Sep 26)
- RE: DOS rules for Nimda Madziarczyk, Jonathan (Sep 26)
- RE: DOS rules for Nimda Richard Ellerbrock (Sep 26)