Re: Detection of hex pattern given directly in a TCP header

[rmkml <rmkml () ligfy org>]

Try stream5 preproc with detect_anomalies enabled,

Could you share a pcap for testing ?

Best Regards
@Rmkml

On Thu, 12 Oct 2017, Yury Markin wrote:

> Rmkml, thank you for the answer!
>
> I want to detect packets with certain values of TCP options, e.g. packets with max segment size (1000) and window scale 
> (0). It would be great if you can advise how this scenario may be implemented.
>
> Best wishes, Ustas.
>
> Чт 12.10.2017 20:34, rmkml пишет:
>       Hi Ustas,
>
>       Yes you are right, is not possible to detect content on tcp header,
>
>       but could you describe more what you want to detect exactly on tcp header please ?
>
>       Best Regards
>       @Rmkml
>
>       On Thu, 12 Oct 2017, Маркин Юрий Витальевич wrote:
>
>             Hello,
>
>             I'm trying to create the Snort rule for detection hex pattern given
>             directly (like "|0a 01 0f 03|") in a TCP header (or IP payload). As far
>             as I know 'content' keyword can not help me because it is used to search
>             hex pattern in a transport layer protocol payload, but not in the
>             payload of network layer protocol. I tried to use 'offset' keyword with
>             a negative value to "move" a cursor to the left of the TCP payload, but
>             this method has failed.
>
>             Is it possible for Snort to detect hex pattern in a TCP header?
>
>             Thanks in advance.
>
>
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