Countersurveillance refers to measures undertaken to prevent surveillance, including covert surveillance. The regiment conducts a wide range of classified activities related to covert surveillance and reconnaissance. These areas may be targets for surveillance and arrests by law enforcement. The Fleet submarines are also capable of surveillance and reconnaissance missions. The airships were used for reconnaissance, surveillance and bombing operations. Some have also taken measures such as installing metal detectors or video surveillance. This was one of a series of cases challenging the NSA warrantless surveillance. This is viewed as a means of preventing mass surveillance by intelligence agencies. Many politicians were jailed or kept under police surveillance. He had a fascination with the idea of mass surveillance, secret police and forced disappearance. It also has original jurisdiction to review warrants for wiretap surveillance. Hyperspectral surveillance is the implementation of hyperspectral scanning technology for surveillance purposes. It is responsible for providing surveillance and control of Canadian airspace. In 1991 two new mechanisms for internal surveillance and control emerged. This is one of the main obstacles of face recognition in surveillance systems.