[Snort-users] snort 2.3.3 --enable-flexresp

hans rosa.schwein at ...12989...
Sun May 1 17:45:01 EDT 2005


i think it's a question of speed. i snooped with ethereal
and found, snort does already send a frame with the reset-flag. 
it has an aknowledgement and sequence number which was 
sent befor from the application. i think, the client does 
ignore this reset, as it would expect a sequence number, which 
is higher, than the last one. 
i did run snort and the network-application on the same server.
it seems, snort is always behind the application.

the problem does not appear without content:"hello"; as snort
has enough time to disconnect. the next frame would come 
much later, if data came from keyboard. 
so no problem for snort to disconnect within certain time.

best regards 


On Mon, Apr 25, 2005 at 10:36:28AM +0200, 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. 
> i searched a lot of time around the internet, but could find 
> any advice, what the problem could be. 
> every advice would be helpfully. 
> just disconnecting any incomming connection could be the idea, a 
> tcpwrapper could this job too. 
> best regards 
> hans 
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