TRIPOLI—On the ground floor of a six-story building here, agents working for Moammar Gadhafi sat in an open room, spying on emails and chat messages with the help of technology Libya acquired from the West.

The recently abandoned room is lined with posters and English-language training manuals stamped with the name Amesys, a unit of French technology firm Bull SA, which installed the monitoring center. A warning by the door bears the Amesys logo. The sign reads: "Help keep our classified business secret. Don't discuss classified...