You still get investigated even if you are a contractor. I know many of them firsthand, and they tell me that contractors are put under additional scrutiny, actually. You need a high-level clearance for this sort of work done on behalf of the government, regardless of your employer.

Glad to know, but I still feel some of contract works require high-level clearance or background check.

If they just need a crack tool, they just need an agent to pay someone to write the tool and that doesn't give away information. Maybe I am spoiled by TV shows how they contact elite hackers in the black market.

Yeah, there's a lot more bureaucracy involved. I know people who used to work at these sorts of places. It's a wonder that anything gets accomplished, at all.