Motion detection systems are used to detect movement in a particular area for the purposes of identifying unauthorized physical access. Such systems typically incorporate sensors that are placed at a building's key entrances and exits in order to monitor ingress and egress. Ingress and egress sensors can use a variety of different technologies to detect motion, but most focus on detecting minute changes in the infrared spectrum. Some sensors are specifically designed to detect the human body's infrared emissions. Others may detect when a strong infrared pattern is being blocked. More advanced sensors can be supported by algorithms that detect any deviation from the established infrared baseline of an area. However the sensor works, if it detects motion, it will likely trigger an alarm or a fail-safe mechanism, such as activating a mantrap.

Bypassing motion detection systems can be tricky, especially if they cover an entire room that you want access to, or if they "block" your path to other rooms of value. The simplest method would be to assess where the sensors are and what zones they are covering, then attempt to move while staying out of the zones (i.e., taking advantage of blind spots). Most sensors are placed in ceilings and opposite of each other to cover the widest possible area. Finding a blind spot is not always feasible if the zones encompass too wide an area or you cannot identify where the sensor is.

Another method would be to place a piece of material, like cardboard, Styrofoam, or glass, over the sensor to block it entirely. If you can't reach the sensor itself, you may be able to use the material to block your own body and minimize the infrared light you are projecting. However, this is not always effective and often requires you to move very slowly and use a large piece of the blocking material. Likewise, sensors that look for strong blocking patterns will not be fooled by either of these tactics.

Some sensors can be bypassed by focusing an infrared or near-infrared light at them. They will not necessarily detect any blocking patterns and the focused light source may be able to mask any human-based infrared emissions. Note that this will not work with sensors that use a baseline comparison.