Beneath the surface: Detecting hidden surveillance in your stay

It's not uncommon to hear about cases of eavesdropping or spying on people who are unaware of it. The problem affects not only celebrities or politicians—it can happen to anyone, even during a hotel or rented apartment stay. One of the tools used in such situations is the so-called "Phenic mirror." Here's how to recognize it.

Even though the summer holidays will soon be behind us, it's worth considering your safety during future trips, whether you plan to stay in a hotel, rented room, or apartment. Fall and winter are approaching, and many of us will take a well-deserved break during this time, whether in the mountains or warmer regions. Unfortunately, not every renter is reliable, which may lead to unethical spying practices on guests. It is worth checking mirrors in this regard.

You can encounter hidden cameras in such places, but even Phenic mirrors. Although these are not very common practices, such cases still occur. A Phenic mirror causes one side to reflect part of the light while the rest passes through (ignoring scattered and absorbed light).

Such a mirror is covered by a thin layer of metal, usually aluminum, and is between two rooms—one brighter and one darker. Its construction allows observing people from one side while remaining unnoticed. They are often used in interrogation rooms but can also appear in other places.

Upon arrival at a hotel or rented apartment, a simple test using a mirror and a marker is worth conducting. Alternatively, you can even use your fingernails. Many video guides on this topic are circulated online.

The test involves placing your fingernail against the mirror surface. The mirror is regular if you see a gap between your fingernail and its reflection. If the fingernail's reflection touches the original, it may suggest a Phenolic mirror. Remember that many factors, such as lighting and material, influence the reflection.

Unfortunately, the described method is not 100 percent effective. It can only suggest a problem with the mirror, which is worth checking in more detail, for example, by talking to the property owner. Additionally, we can use a smartphone and its flashlight. After turning off the lights in the room, point the flashlight at the mirror. In the case of a Phenic mirror, we might see through it to the other room or a hidden camera.

While staying in a hotel during a trip, it is worth checking if a hidden camera is not watching us. This is generally difficult, but a few methods can help. Firstly, it is worth thoroughly checking all suspicious devices in the room, such as clocks, smoke detectors, or electrical outlets. These may contain spy cameras. It is also worth using smartphone applications that detect Wi-Fi signals from cameras. If something raises suspicion, it should be reported to the hotel staff immediately.