[jason taylor]

I don't know if this is relevant but Stuxnet used at least five undiscovered exploits and perhaps quite a bit more (apparently the launcher was hoarding them) to break it's target. As it was not on the normal network it had to rely on old fashioned sabotage techniques (outright traitors and just plain sluggards about security) to get through.

It would be interesting to know how long Whoever It Was (we would never do that) spent casing the target.