Re: Advice on multiple packet capture

["pieter claassen" <pieter () claassen co uk>]

Yes, I agree. What you need to do is write two sets of rules that are
statefull:

Something like this:
Rule1: uricontent:a.jpg; flowbits:set, ajpg.seen; noalert
Rule2: flowbits:isset,ajpg.seen, uricontent:b.jpg; msg: "saw a.jpg and then
b.jpg"
Rule3: uricontent:b.jpg; flowbits:set, bjpg.seen; noalert
Rule4: flowbits:isset,bjpg.seen; uricontent:a.jpg; msg: "saw b.jpg and then
a.jpg"

Regards,
Pieter

On Mon, Jan 12, 2009 at 10:23 PM, jeffs <jeffs () speakeasy net> wrote:

> I've been using Snort and still consider myself a newbie although I am
> fairly familiar with writing basic rules.  Unfortunately, the feat I
> need to perform may need a more advanced set of eyes so I am hoping
> someone on this list may be able to help me out.
>
> I need to get only 1 alert on two separate GET requests that contain
> different .jpg file names.
>
> For example, there is a web page, it contains A.jpg and B.jpg.  If
> someone looks at it I want to be able to get one alert but NOT if they
> look at a different page which contains A.jpg and NOT B.jpg or still yet
> a different page that contains B.jpg and NOT A.jpg.  Only on the page
> the contains BOTH .jpgs should generate 1 alert.
>
> I've tried the within keyword but I believe this only searches within a
> single packet and as the two separate jpg files are sent via two
> separate GET requests, I believe I am working with more than one packet,
> am I correct in that assumption?
>
> thanks for any advice.
>
>
>
>
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