[Snort-sigs] sid:13272; rule is not so good

Miso Patel miso.patel at ...2420...
Tue Dec 6 15:59:52 EST 2011


Thanks you.  I am not sure what SEU is but this (along with year end
projects and future planning for 2012/goals) has got me thinking ...
why then did this rule make it into the release to begin with?  What
UAT does the rules go thru?

For a while now I have been thinking about and have not yet pulled the
trigger on the Emerging Threats Pro rules?  Does anyone have
experience with these or recommend them?  I am getting tired of my
engineers coming to me and showing such bad snort performance
profiling from VRT rules.  There has to be a better way and I don't
have the staff/budget to hire my own IDS QA special engineer right
now.

Thanks.

Miso, CISO

On 12/6/11, rmkml <rmkml at ...174...> wrote:
> Hi Miso,
> Can you upgrade this rule to last revision (5) please?
> Appear on SEU 501 at 22 sep 2011.
> Regards
> Rmkml
>
>
> On Tue, 6 Dec 2011, Miso Patel wrote:
>
>> My engineers say rule sid:13272; is not performing good.  Here is it:
>>
>> misc.rules:alert tcp $EXTERNAL_NET $HTTP_PORTS -> $HOME_NET any
>> (msg:"MISC Microsoft Windows ShellExecute and IE7 mailto url handling
>> code execution attempt"; flow:to_client,established;
>> content:"mailto|3A|";
>> pcre:"/[^\n]*?[\x25\x22]\x2E(com|bat|cmd|exe)/Ri"; metadata:policy
>> security-ips drop, service http; reference:bugtraq,25945;
>> reference:cve,2007-3896;
>> reference:url,www.microsoft.com/technet/security/advisory/943521.mspx;
>> reference:url,www.microsoft.com/technet/security/bulletin/ms07-057.mspx;
>> classtype:attempted-user; sid:13272; rev:3;)
>>
>> They say it is just a 'mailto:' match (which seems common with the web
>> pages these days) and then a "Regular Expression" which is causing our
>> sensors to not like it and CPU is consumed.
>>
>> I know we run a slightly older rules (due to antiquated hardware,
>> corporate bureaucratic red tape, etc.) but are all these rules so bad?
>> My engineers say this is not good and I wonder if we are detecting on
>> what we need to or if there are dropped packets due to so much bad
>> rules using CPU and RAM?  Is there a better rule list I can use for my
>> sensors?
>>
>> Thank you.
>>
>> Miso, CISO
>




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