Re: RE : Help with signature - offset

[miha rass <miha4246 () gmail com>]

Thanks for the input.  I figured it out.

I was looking to trigger off the first few bytes of the TCP payload, so by
putting offset:0 it work.  I am not sure why it works b/c the content data
is sitting at offset:54 according to wireshark.

I am guessing that content ONLY works within the TCP payload, not in the
eth/ip/tcp header.

Does anyone know if wireshark adds or removes any data while parsing?


On Tue, Jul 23, 2013 at 1:54 AM, rmkml <rmkml () yahoo fr> wrote:

> Hi Miha,
>
> Don't tested but can you try with offset:4; please ?
>
> Because here it's a payload offset.
>
> Regards
> @Rmkml
>
>
>
>
> -------- Message d'origine --------
> De : miha rass <miha4246 () gmail com>
> Date :
> A : snort user list <snort-users () lists sourceforge net>
> Objet : [Snort-users] Help with signature - offset
>
>
> Hello,
>
> I am trying to id why my test snort sig wont fire from the offset.  I have
> a generic sig that I have tested from flow, depth, content etc.  It all
> works but the offset.
>
> I am testing the sig against some old gh0st rat traffic.  below is the
> sig.  I thought the tcp payload would start at offset 54.  The content in
> the hex is in bold.
>
>  Alert tcp any any -> any 21 (msg:"testing for gh0st"; content:"v2010";
> offset:58; nocase; sid:100000939;)
>
>
> 0000  00 50 56 e3 19 d5 00 50  56 3c f6 41 08 00 45 00   .PV....P V<.A..E.
> 0010  01 31 02 74 40 00 80 06  bc ce c0 a8 6a 8d 79 3f   .1.t@... ....j.y?
> 0020  96 0f 04 34 00 15 04 4a  7e 7d 59 4f 74 3a 50 18   ...4...J ~}YOt:P.
> 0030  fa f0 5d c1 00 00 76 32  30 31 30 09 01 00 00 fc   ..]...*v2 010*
> .....
> 0040  00 00 00 66 00 00 00 9c  00 00 00 05 00 00 00 01   ...f.... ........
> 0050  00 00 00 28 0a 00 00 02  00 00 00 53 65 72 76 69   ...(.... ...Servi
> 0060  63 65 20 50 61 63 6b 20  32 00 00 3f 9b 91 7c d8   ce Pack  2..?..|.
> 0070  c0 97 7c eb 9a 91 7c 30  f4 40 00 90 fe ab 00 ff   ..|...|0 .@......
> 0080  ff 00 00 00 c0 fd 7f a8  34 24 00 ff ff ff ff 12   ........ 4$......
>
> Thanks
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