A method and device for omnidirectional and anti-sabotage anti-tampering detection are disclosed. For this purpose, a proposed security device assembly includes a mounting bracket, a security device such as a motion detector or surveillance camera, and an anti-tampering system. The security device is mounted via the mounting bracket. The anti-tampering system includes a permanent magnet and a magnetometer for detecting a magnetic field of the permanent magnet, and includes a controller. The controller detects changes in the magnetic field that are indicative of movement between the mounting bracket and the security device. In general, the anti-tampering system spans across the mounting bracket and the security device. Preferably, the permanent magnet is attached to the mounting bracket and the magnetometer is included within the security device.