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From: Jeremiah Grossman (jeremiahwhitehatsec.com)
Date: Tue Jan 15 2002 - 13:09:17 CST
The Owasp Project wrote:
> As you know we are going to capture a topic a week
> and compile the best knowledge into some of the
> testing Framework sections at www.owasp.org. So this
> weeks topic is Black Box vs White Box testing.
> What is black box and white box testing;
My take is that "black box" you know nothing about the system
and "white box" is you know or have access to everything within
the box. Easy enough.
> when is it appropriate to use one or the other; should you do
> both; what can you find with one that you can't find
> with another;
In my experience systems have different needs and expectations
on security or how secure something needs to be. These expectations
can range from "Low".. to "Decent"...to "High"...to......
So, the type of pen-tests one should perform should reflect the
security needs of the system or who the system needs to be protected
Generally speaking, if a modest level of security required
to protect against "outsiders", then a thorough "black box" test
should be a good choice. Remember, even after a great
"black box" test, system insecurity may still exist and commonly
do... this is why only expect a "modest" level of security
as a result.
If the system requires an increased level of security above
the "black box" test, then a "white box" test is a good choice.
This type of test will uncover many more system insecurities and
instabilities that cause weaknesses than a "black box" test will.
Many times "white box" tests are done during a QA phase.
Then, when you need the best measures.... employ both
"black box" and "white box". "white box" the system
to secure it.... then "black box" to estimate the effectiveness.
Done with the babble so, my take....
"black box" == "modest security evaluation"
"white box" == "better security evaluation"
"black box + white box" == "best security evaluation"
> is one more skilled; does one cost
> more to do; does one take longer; which one produces
> better results etc
Its hard to say what requires more skill.... what one can say
that whatever method is employed "due diligence" should
be assumed. "white box" testing does indeed take the
longest and does produce the best information feedback
to help increase the security of the system.
Again though, whatever methods are employed, they
always should reflect the needs of the system.