It's also interesting when the client provides documentation, but things like the network diagrams are out-of-date and inaccurate. It's like starting with negative information; starting from scratch would put you ahead in those situations
...aaaannnnnddddd that's EXACTLY why I prefer Blackbox to Whitebox tests, any day. I'd rather figure it out for myself (since over 50% of the time I have to, anyway,) and have a little more say in things.
Obviously, there are the times where they limit your scope, so you kind of HAVE to deal with their information, but...
GCIH - GIAC Certified Incident Handler : Passed my GCIH
