[Snort-users] [Emerging-Sigs] sensitive data pre-processor

Joel Esler jesler at ...1935...
Wed Sep 29 14:03:42 EDT 2010

I've had the SDP successfully deployed in a number of areas.

The reality of the situation is, like Brad said below, it detects strings of
numbers.  Yes, there is some intelligence to the format of the numbers and
how they start and end and things like that, but there are just basically
strings of numbers.

I've seen HTTP cookies, url's, webpages, etc fire on the SDP.  I've also
seen SSNs, credit cards, and lots and lots of legit stuff trigger on them as

So your milage may vary as far as the SDP is concerned.

Example:  Where I've gotten my most value for the product is in a clean
(no-web-traffic environment) where the customer was not aware of the content
of traffic, and come to find out the traffic as laden with SSNs and credit
cards (much to the behest of the customer.)


On Wed, Sep 29, 2010 at 1:35 PM, Tilley, Brad <rtilley at ...14863...> wrote:

> > is anyone else getting FPs with the sensitive data pre-processor?
> Yes, but that is to be expected.
> > every single firing i've seen of the sensitive data rules has been a
> > false
> > positive and always apparently related to the serialization numbers
> > used in web
> > forms on forums and social networking sites...
> Same here, but again, that should not be surprising.
> > currently i have the SDF email addresses and social security numbers
> > (w/out
> > dashes) disabled... i've had numerous firings on the social security
> > numbers (w/
> > dashes) rule, too, but have not yet disabled it...
> >
> > it is especially telling when the SSN rules fire on sites that have no
> > SSN data
> > on them or those that do but it has never been given...
> Basically, *any* nine digit number is a SSN (with a few notable
> exceptions)... some day 123-45-6789 will be issued in NY State.
> Go here to test numbers (Only enter fake numbers or generated test data):
> http://16systems.com/numbers
> So let's say that NY issued 123-45-6789 to John Doe. You may see
> 123-45-6789 in lot's of places, and that string is indeed a valid SSN, but
> not in the context of a website that has nothing (at all) to do with John
> Doe. Snort isn't doing context validation. It does not know that John Doe's
> name is not on the website, it just sees 123-45-6789 and triggers (as it
> should).
> I wrote Find_SSNs/CCNs (years ago) for Virginia Tech. I'm used to dealing
> with this sort of thing. At best, you'll have 90+ percent false positives
> when dealing with US SSNs. Now, what *did* surprise me about Snort's
> preprocessor was the FP rate on CCNs, that was way more than I've dealt
> with. My experience with SSNs and CCNs has always been that CCN detection is
> far, far more accurate, but that is not the case with the new preprocessor.
> Brad
> > can the SDF decode encoded strings and may it possibly be detecting
> > sensitive
> > data in there??
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