[Snort-users] reading tcpdump file

Edward Young ey52 at ...2868...
Tue Oct 12 07:10:38 EDT 2004


Thanks for the suggestions but neither worked.  There were no preprocessors. 
I only had that one rule in my conf file.

So am I getting problems because the packets are incomplete?

I tried "alert tcp any any <> any any (content:"get"; nocase;)" on the 
tcpdump file but didn't get any alerts on that file.

I checked the tcpdump file in Ethereal and did find packets with "get" in 
the payload but they were marked as "Short Frame".  Does snort handle these 
"Short Frame" packets differently from complete packets?

Thanks,

Edward Young

----- Original Message ----- 
From: "Jeff Dell" <jdell at ...1095...>
To: "'Edward Young'" <ey52 at ...2868...>; 
<snort-users at lists.sourceforge.net>
Sent: Monday, October 11, 2004 7:36 PM
Subject: RE: [Snort-users] reading tcpdump file


> We had this same problem on our honeynet and had to start a new snort
> process that was dedicated to tcpdump. What you are seeing can be caused 
> by
> a few different reasons... here are a couple:
>
> 1. It is not logging the fragmented packets, but the reassembled packet. 
> If
> you only want to log tcp traffic, you might want to turn off the
> preprocessors. However this should be fixed in the newer versions of 
> Snort.
>
> 2. You might not be capturing both sides of the transmission. I would try
> this:
>  alert tcp any any <> any any
>
> Cheers,
>
> Jeff
>
> -----Original Message-----
> From: snort-users-admin at lists.sourceforge.net
> [mailto:snort-users-admin at lists.sourceforge.net] On Behalf Of Edward Young
> Sent: Monday, October 11, 2004 6:23 PM
> To: snort-users at lists.sourceforge.net
> Subject: [Snort-users] reading tcpdump file
>
> Hi,
>
> I am trying to read a tcpdump file into snort.  For some reason, it seems
> that some of the tcp packets are being ignored for some reason.  The only
> reason I can think of is because the tcpdump file only captured at most 96
> bytes of each frame.
>
> The only rule I have in my config file is "alert tcp any any -> any any" 
> and
>
> these are the results that I get:
>
> Snort processed 37298 packets.
> ============================================================================
> ===
> Breakdown by protocol:
>    TCP: 32827      (88.013%)
>    UDP: 475        (1.274%)
>   ICMP: 32         (0.086%)
>    ARP: 3176       (8.515%)
>  EAPOL: 0          (0.000%)
>   IPv6: 4          (0.011%)
>    IPX: 7          (0.019%)
>  OTHER: 531        (1.424%)
> DISCARD: 246        (0.660%)
> ============================================================================
> ===
> Action Stats:
> ALERTS: 32621
> LOGGED: 32621
> PASSED: 0
>
> Where do those remaining 206 packets go?  They are tcp so why aren't they
> logged?  I'm thinking that those 206 frames are the frames that are
> incomplete.
>
> Thanks,
>
> Edward Young
>
>
>
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