|Federal Bureau of Investigation|
The Federal Bureau of Investigation, or FBI for short, is the domestic intelligence and security service of the United States of America, and its principal federal law enforcement agency.
It is also possible that Susan Choi was an F.B.I. agent since the F.B.I. is the agency that handles domestic threats to the United States. However, it was never specified in Spider-Man which armed federal agency Susan Choi worked for.