Snort mailing list archives

Snort Evasion?


From: IDS Expect <robertgoldman2000 () yahoo com>
Date: Sun, 17 Mar 2002 14:28:41 -0800 (PST)

Hi,

I have been examining the snort 1.8.4 source code and
I think I found a very simple way to evade Snort if
and when stream4 is in use.

It seems like in spp_stream4.c, FlushStream() will
ignore all packets if base_seq is zero. Well, base_seq
is set to the sequence number of the first data byte.
What if the attacker initializes her TCP connection's
sequence number to 0xffffffff. This well make base_seq
zero and Snort will further ignore any data on this
connection.

Am I right?
--rob 


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