Re: Question about searching in packet headers

[Santosh Subramanya via Snort-sigs <snort-sigs () lists snort org>]

Hi Fedor,

To search in TCP header, you can use alert ip $EXTERNAL_NET instead of alert tcp EXTERNAL_NET.

By using ip instead of tcp, snort starts searching patterns mention in signature from ip header.

I hope this helps.

Regards,
Santosh

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________________________________
From: Snort-sigs <snort-sigs-bounces () lists snort org> on behalf of Fedor Niskov via Snort-sigs <snort-sigs () lists 
snort org>
Sent: Sunday, October 18, 2020 12:16:24 AM
To: snort-sigs () lists snort org <snort-sigs () lists snort org>
Subject: [Snort-sigs] Question about searching in packet headers

Hello, excuse me, I have a question about Snort rules: can I do search in packet headers? I know about the 'content' 
option, but it performs searching only in payload; however, I'd like to check presence of some byte sequences in 
headers.

It would be useful to search in headers; for instance, I need to check some TCP options, but Snort non-payload rule 
options don't support it; if I could search for specific bytes in TCP header, I would be able to perform these checks.

(Fedor Niskov)

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