How to Acquire a Black Site Key. The only way to acquire a Black Site Key is to successfully complete a Stronghold by yourself or as part of a team. As such, you'll need to defuse the bomb at any given Black Site, and be the first person/people within the match to do so.
CoD4 is still a lot of fun. Plenty of people still play it, and most of the servers have more then enough players to play properly. I can join my favorite server in 10 sec.