Snort mailing list archives

Re: historical rule information?


From: "Miller - CDLE, Michael" <michael.miller () state co us>
Date: Thu, 18 Apr 2013 11:25:52 -0600

Thanks Patrick, I'm beginning to think it's a false positive. The top
destinations are all Akamai in nature, and I'm beginning to think there's
something specific about the originating site that's causing the alert.
We're providing internet access to a couple dozen recipients of similar
size, and this is the only one generating that traffic.


On Thu, Apr 18, 2013 at 10:57 AM, Patrick Mullen <pmullen () sourcefire com>wrote:

Michael,

Thank you for your query.  That rule is known to have issues with
false positives so it is not enabled in any default policies, which
means it is disabled by default.  The proper replacement for this
alert is from a preprocessor, which has more contextual information
surrounding the event that is possible within the rule --

129:15:1 Reset outside window

(That is sid 15 of preprocessor 129, Stream5).

Regarding your statement "There are two ISA servers on that network,
and they've been patched according to the KB article referenced in the
rule detail, but the alerts are still being generated," the rule has
no way of knowing that your servers are patched.  This is part of
tuning your IDS policy -- if you know your servers are not susceptible
to this three year old attack, disable the rule to improve performance
and reduce unnecessary alerts.


Thanks,

~Patrick

On Thu, Apr 18, 2013 at 11:55 AM, Miller - CDLE, Michael
<michael.miller () state co us> wrote:
I'm hunting down a rule that's generating a LOT of traffic on our network
and was wondering if there were a wiki or history of rules to see what
the
thinking was behind them. Specifically, I'm alerting on

[3:15474:5] BAD-TRAFFIC Microsoft ISA Server and Forefront Threat
Management
Gateway invalid RST denial of service attempt [Classification: Attempted
Denial of Service]

There are two ISA servers on that network, and they've been patched
according to the KB article referenced in the rule detail
(http://technet.microsoft.com/en-us/security/bulletin/MS09-016), but the
alerts are still being generated.


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--
Patrick Mullen
Response Research Manager
Sourcefire VRT




-- 
*Michael Miller*
*Network Security Engineer - SECOPS*
*
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analytics on semi-structured data. The platform includes APIs for building
apps and a phenomenal toolset for data science. Developers can use
our toolset for easy data analysis & visualization. Get a free account!
http://www2.precog.com/precogplatform/slashdotnewsletter
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