Re: Performance Question - content vs uricontent

[Matt Olney <molney () sourcefire com>]

URICONTENT is the prefered method for a pair of reasons:

1)  You're looking at a smaller set of data, so your match (or lack
thereof) will be faster
2)  You're looking at a specific set of data (the URI) so your match
(orlack thereof) will be more accurate and less prone to false
positives.

Also, some other notes:

1)  Your "POST" match would not be in uricontent.
2)  Your depth 69 is evadable by ../../../../.. tricks, as content
isn't normalized for URI traffic.

Also, if you're going to write a rule requiring POST, upgrad to snort
2.8.3 and use the http_method modifier, and look simply for POST.
Same arguments as the top....faster and more accurate.

Hopefully something in there answered your question.

Matt

On Fri, Jan 30, 2009 at 12:16 PM, dxp <dxp2532 () gmail com> wrote:
> The following snippet was taken from Emerging Threats mailing list
> discussion regarding optimizing one of the rules.  Can someone here shed
> some light into this?
>
> --- snip --- by Martin Holste
>
> but academically speaking, can anyone say which is theoretically less load?
> For instance, in the below example, which would be faster:
>
> content:"POST "; depth:5; content:"/forms.cgi"; within:64;
> (or some other smallish integer to keep from scanning the entire flow)
>
> or
> content:"/forms.cgi HTTP"; depth:69;
>
> or
> does uricontent beat them both?
>
> --- snip ---
>
> -
> -=[ dxp ]=-
> 0xA3F3C6E3
>
>
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