[Snort-users] Are the rules not being read?

Alex Kirk akirk at ...1935...
Mon Apr 26 07:47:20 EDT 2010

Are you running Snort on the same machine that's doing the chatting? Most
operating systems do something called TCP checksum offloading, where the
checksum is calculated on the network card on the packet's way out to its
destination. Since Snort will snag the packet from libpcap before it hits
the network card, the checksum will not have been calculated yet, and will
thus be incorrect.  Since Snort's default behavior is to ignore packets with
broken checksums, it will not alert on these packets. Try running with "-k
none" to skip checksums and see if that fixes things.

On Apr 26, 2010 3:19 AM, "Eric Zheng" <zhengeric at ...125...> wrote:

 I have set up snort successfully and I can get it to read pings to websites
and scan packets.  However, I am testing out the chat rules which should
trigger an alert whenever I sign onto MSN or Yahoo but it does not seem to
do anything whenever I sign in and talk to people.  I have it enabled in
snort.conf (took away the # sign) and see that chat.rules is in the rules
directory.  Anyone know any possible causes of this?  Thank you.

PS:  I'm also getting a lot of 1384 "malformed advertisement" alerts which I
believe to be false positives.  Any way to correct this?  Thanks.

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