How did insurgents know the *covert* CIA facility location?

I don't recall it being explained how the insurgents knew of the CIA annex yet how could they not know? The walled off compound inhabited by Americans was surrounded by locals and had employees who were locals. I'm sure it was quite obvious to the neighboring Libyans the annex was some type of American military or quasi-military base.




He killed sixteen Czechoslovakians. Guy was an interior decorator.

It was supposed to be a front for an oil executive, but I did not understand why it had a big sign on the gate that said something like "United States of America Special Operations"...

It was stated that the insurgents thought it was another lightly armed target and were caught by surprise during the first attack on the compound.

The big sign was on the fence of the first location that was attacked not the CIA facility. I made the mistake at first as well.