RE: Of the three expensive vulnerability scanners

["King, Stuart (REHQ-LON)" <Stuart.King () reedelsevier com>]

There's a lot of criticism in this group of the vulnerability scanners - and
no they are by no means a panacea for application security - but they ARE
useful. I also argue that they are getting better (I regularly make use of
one of "big 3").

What I will state is that used by themselves by a person with no other
skills in pen testing web applications that they are next to useless - but
then I would argue the same for tools such as Nessus et al. It's how you
interpret and report the results and how you focus attention on the parts of
the application which the scanners are not yet mature enough to reach. 

I would also not recommend using (excellent) training tools such as Hackme
for testing the effectiveness of the scanners - it is not coded as any live
application would be. If you want to baseline, then the only way really is
to code review a production site and work out the vulns manually first then
see how many the scanner detects. 

Vulnerability scanners should be just one of an arsenal of tools for the
good security tester. The best tool of all is the mark one eyeball..

-----Original Message-----
From: Adam Shostack [mailto:adam () homeport org] 
Sent: 21 November 2004 19:47
To: ban.marketing.bs () hushmail com
Cc: webappsec () securityfocus com
Subject: Re: Of the three expensive vulnerability scanners

I know of companies that deploy millions of lines of new code
annually.  (Both in house and outsourced code)  Deciding what to have
an expert look at is hard and slow.  Adding any automation makes their
experts more effective.

So you need do decide between static testing, dynamic testing, or some
mix.  Static testing is very good at finding some things, but not
others.  It finds strcats, but doesn't find a lack of authentication.
(I like to think of these as sins of commission vs. sins of
ommission.)

I'm not going to argue for or against the commercial dynamic test
tools...I just don't know enough about them.  But dynamic testing is
not fundamentally flawed, its a potentially useful part of a toolset.
Would you not nmap and nikto boxes before they go out, just as a
sanity check?

Adam


On Tue, Nov 16, 2004 at 06:14:28PM -0800, ban.marketing.bs () hushmail com
wrote:
| OK what am I missing here? Why use a fundamentlaly floored 
| technique for finding the issue? Why not look at the source? Its 
| pretty damn obvious where you are reading or writing unvalidated 
| data....please please no "source is not always available" 
| junk.....this is the web and 99% your looking at bespoke apps. You 
| have to ask or educate the client at worse. 
| 
| Its about time the industry started taking software security 
| seriously and continuing down this futile route of refining pen 
| testing techniques to make up for the obvious limitations of this 
| technique is not it IMHO.
| 
| Newsflash - Most serious XSS issues in the real world are stored 
| not refelcted and unless you can trace data to the reflection point 
| this technique will NEVER find them ! 
| 
| 
| 
| In-Reply-To: <003801c4c9c6$e5f39530$8d8606d1@rockstar>
| 
| Jim,
| 
| The problems you've mentioned with regard to the Cross Site 
| Scripting tests
| point to a functionality area where the major players in the App 
| security
| market need major improvement. As Jeremiah pointed out, the problem 
| is
| broader than XSS policies alone, but it certainly affects them. 
| 
| One reason the XSS policies yield diminishing returns and are 
| poorly
| organized in reports is due in part I believe to a lack of proper 
| detection
| mechanisms. Both products use a plethora of fault injection 
| techniques, yet
| neither seems sensitive to whether or not the injected script is 
| returned
| within the context of the app's response in a form that is 
| executable by a
| browser. As a result, when one form field is vulnerable to XSS, you 
| can get
| into situations where virtually every XSS test returns with a 
| positive
| detection.
| 
| As you've no doubt noticed, each product checks for various kinds 
| of XSS,
| some of these kinds are distinguished on the basis of the delimiter 
| that is
| used. Despite the technical differences, each delimiter type has a
| sophisticated name (i.e Double Quote Single Quote Bracket kung fu, 
| etc.)
| 
| ">&lt;script ....
| '>&lt;script ....
| ">">&lt;script ...
| <--&lt;script ...
| <textarea>&lt;script ...
| etc.
| 
| While the main vulnerability condition is whether or not an 
| application will
| "echo back" the script sequences, real problem is that the 
| different
| delimiters are important because some will execute when returned by 
| the
| application, and others will not, depending upon the HTML/Script 
| code of the
| application. This is why it is important to audit the application's 
| logic,
| but there really is no reason to test for 12 different types of 
| cross site
| scripting scenarios using different delimiters and script types if 
| the
| detection mechanism can't account for which sequences actually 
| yield results
| that are executable. 
| 
| The optimal solution in my opinion would be to emulate a browser 
| and trap
| for alerts (or other events) and then to organize the report data 
| based on
| which delimiters successfully generated the desired pop-ups (or 
| whatever
| event is trapped for). The rest could be classified as warnings. 
| This would
| help to minimize the multiple alerting problems that plague the XSS 
| tests
| and produce frequently confusing results. While this wouldn't fix 
| the
| reporting problems, it would help to attenuate the signal.
| 
| -tom
| 
| 
| 
| 
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