Snort mailing list archives
Re: snort 2.3.3 --enable-flexresp
From: Matt Kettler <mkettler () evi-inc com>
Date: Mon, 25 Apr 2005 11:35:49 -0400
hans wrote:
hi all i tried the experimental feature '--enable-flexresp' for compiling snort 2.3.3 on solaris 9 ( both sparc and intel plattform ) the first tests did run well, the following rule did disconnect an incomming connection immediate: alert tcp any any <> $HOME_NET 25 (msg:"HELLOon25"; resp:rst_all; ) the next step was to modify this rule sligthly. the disconnect should only appear, if the word "hello" was seen, with this rule: alert tcp any any <> $HOME_NET 25 (msg:"HELLOon25"; content:"hello"; resp:rst_all; ) i telnet to port 25, key in "hello" ( knowing it's not a smtp-dialog ) and nothing happens. i get a logentry, so the rule is involved if the word "hello" is seen, but no disconnect.
When you use a telnet client to generate test traffic, the telnet client will generally send one TCP segment per character because the telnet client explicitly disables the nagle algorithm. Since you are typing it out by hand, the string is actually sent so slow that the mailserver has a chance to acknowledge every individual character. Snort's stream re-assembly flushes whenever an ACK packet from the server comes by. Thus, each individual character was probably run through the rules engine separately, instead of as a single string "HELLO" Try using something like netcat instead of telnet, which more realistically simulates network traffic. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ 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:
- Snort 2.3.3 available Jeremy Hewlett (Apr 23)
- Re: Snort 2.3.3 available Eric Maheo (Apr 24)
- Re: Snort 2.3.3 available James Riden (Apr 26)
- snort 2.3.3 --enable-flexresp hans (Apr 25)
- Re: snort 2.3.3 --enable-flexresp John C. Silvia (Apr 25)
- Re: snort 2.3.3 --enable-flexresp hans (Apr 27)
- Re: snort 2.3.3 --enable-flexresp hans (Apr 27)
- Re: snort 2.3.3 --enable-flexresp Matt Kettler (Apr 25)
- Re: snort 2.3.3 --enable-flexresp Matt Kettler (Apr 25)
- Re: snort 2.3.3 --enable-flexresp Rich Adamson (Apr 26)
- Re: snort 2.3.3 --enable-flexresp hans (Apr 27)
- Re: snort 2.3.3 --enable-flexresp John C. Silvia (Apr 25)
- Re: snort 2.3.3 --enable-flexresp hans (May 01)
- showing payload hans (May 08)
- Re: Snort 2.3.3 available Eric Maheo (Apr 24)
- <Possible follow-ups>
- RE: Snort 2.3.3 available Harper, Patrick (Apr 26)