Snort mailing list archives
many rules with good fast_pattern vs. single rule with pcre
From: Duane Howard <duane.security () gmail com>
Date: Mon, 29 Dec 2014 12:43:14 -0800
I'm writing some rules, and I find myself asking a question that's probably been answered, but my searching isn't turning up something obvious. In looking at a set of malware samples the only consistent pattern that can be used for all variants is a bunch of null bytes. This is a pretty poor fast pattern, and this alone makes for a large number of FP's. Adding another match to the rule can be done, but there are ~20 variants for the next byte match, these are good fast_pattern matches from my basic testing. My question, is whether it's better to have 20 rules with a good fast pattern, or one rule with a mediocre fast pattern and a pcre covering the 20 variants? This is another instance where I find myself wishing flowbits were taken into consideration *before* entering full rule evaluation, etc. ./d
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Current thread:
- many rules with good fast_pattern vs. single rule with pcre Duane Howard (Dec 29)
- Re: many rules with good fast_pattern vs. single rule with pcre Joel Esler (jesler) (Dec 29)