The suggestion that Mary Lou McFate was a double agent is contained in a deposition filed as part of a contract dispute involving a security firm. (more)
The employee double-cross is an old and highly successful trick. Aside from the obvious, undercover employees also have the time and opportunity to plant bugs and wiretaps. If an employee-spy is discovered be sure to conduct a thorough bug sweep after they are fired. Better... Conducting thorough bug sweeps on a regular basis is a good way to uncover the undercover spy.