Abstract: An apparatus for preventing the removal of cassettes from an automated teller machine along their guide paths includes mountings and a plurality of retainers, each associated with its respective cassette. Each retainer is securable in an operational position on the mountings to extend into the guide path of its respective cassette to prevent removal of the cassette. Further, each retainer is movable from the operational position to allow removal of its respective cassette. The retainers may be removable from the mountings to allow removal of the cassette and lockable to the mountings. Two or more locking devices may be used in which the locks are operated separately or remotely. The retainer may be a suitably shaped elongate member such as a locking bar. Multiple bars can be used to retain a cassette. The retainers may guard the face of the cassette.