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Bypassing Doors – Part 3: REX Sensor

Let’s bypass another door we don’t have access to! The Bypassing Doors blog series demonstrates easy-to-use tools and techniques that can be utilized to bypass an organization’s interior and exterior doors. In this part 3 post, we will be talking specifically about utilizing a piece of paper! What?!?! Yep! That is exactly what I thought at first – but a simple piece of paper will bypass your building’s door.

More often than not, buildings are equipped with a “Request to Exit” sensor, or REX sensor. These sensors are implemented due to various regulations and building code requirements.

Request To Exit Motion Sensor

The images below show the Request to Exit sensor (REX sensor) and the way it looks on a door. Typically, these sensors make use of Passive Infrared (PIR) for detection of motion. PIR detects changes in temperature within the area of its field of view. A piece of paper can be tossed under the door frame and creates a sense of motion that triggers the sensor. This opens the door and allows one access inside – WITH ONLY A PIECE OF PAPER!

Photo of a Request to Exit sensor (REX sensor):

A Request to Exit sensor (REX sensor)detects motion, screen grab by White Oak Security

Photo of a Request to Exit sensor installed above a door:

Image from White Oak Security’s blog of a Request to Exit sensor (REX sensor) installed above a door.

Pictured below the bypassing tool, a terrifying stack of paper!

Pictured in White Oak Security’s blog is a bypassing tool, a terrifying stack of paper!

Paper REX Sensor Bypass

Here is a video of bypassing a REX sensor door with a piece of paper:

video of bypassing a REX sensor door with a piece of paper

How To Prevent Paper Bypasses

There are multiple prevention options that can be implemented to prevent bypassing with paper. These options include the following:

Moving The REX Sensor 

By moving the REX sensor further away from the door, it can prevent the trigger from sensing indirect motion.

Kick Plates

Install kick plates to prevent items like paper, from sliding items under your doors by minimizing any gap beneath the door.

Rubber Moldings

Implement rubber moldings to prevent unauthorized tools, like paper, from sliding under the door.

Door Shoes

Like rubber moldings, the door shoe adjusts to prevent anything from being shoved under your door.

More Bypassing Doors

If you missed part 1, check out the UTDT post. Here’s part 2, the DDT post. More physical pentesting tools and bypassing overviews are being published soon, so stay tuned for part 4!


White Oak Security is a highly skilled and knowledgeable cyber security testing company that works hard to get into the minds of opponents to help protect those we serve from malicious threats through expertise, integrity, and passion. 

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