An anti-tamper assembly is provided in order to sense the attempted removal of a body attached to a surface by a fastener. The assembly includes an anti-tamper access-blocking element positioned in an anti-tamper position proximal to the fastener, along with an anti-tamper switch operably coupled with the element in order to bias the switch to one switch condition. In the event that the element is moved from its anti-tamper position, the switch moves to another switch condition, which generates an alarm signal. The assembly may be used to protect an alarm section forming a part of an alarm assembly. The section includes a sensor or switch operable to detect relative movement between first and second members such as a door and doorframe. A mechanically actuatable switch having an actuating arm may be used where the arm engages access-blocking element.