Consumer devices designed to find hidden cameras, microphones and other surveillance equipment may not provide the protection people expect.
A new study found that ordinary users equipped with these detectors still missed nearly 60% of hidden surveillance devices.
Researchers led by University College London (UCL) tested 19 commercially available detectors to see how well people could use them in realistic situations.
The findings were presented at the USENIX Symposium on Usable Privacy and Security.
Hidden surveillance equipment has become increasingly easy to buy. Cameras, microphones and GPS trackers can be disguised as everyday objects, including clocks, USB chargers, smoke alarms, picture frames and toys.
Although such devices may be marketed for security purposes, they can also be misused to secretly monitor people. Researchers are particularly concerned about their use in domestic abuse, where covert surveillance can become part of coercive control and other forms of abuse.
Consumer detectors promise to help people discover these devices. Many work by identifying radio-frequency signals or other signs of electronic equipment. But the researchers found that operating them—and understanding what their readings actually mean—can be surprisingly difficult.
The study involved 34 people from different backgrounds. Participants searched simulated living rooms filled with furniture, electronics and other household objects while researchers concealed surveillance equipment around the rooms.
Using a commercial detector helped only slightly. Participants with detectors missed 58.8% of the hidden devices. When participants searched using only their eyes, they missed 66.7%.
The researchers concluded that technical detection ability wasn’t the only problem. Many detectors displayed signal strengths, radio frequencies and technical terms without clearly explaining what users should do with that information.
One type of technology performed considerably better: smartphone apps designed to identify Bluetooth trackers such as Apple AirTags. Participants using these tools missed 27.6% of devices and recorded no false positives.
The researchers believe usability was a major reason for the difference. Instead of simply telling users that a wireless signal existed, the apps could identify recognizable devices, allowing people to investigate whether a detected object was suspicious.
Confusing detectors can also have emotional consequences, the researchers warned.
A false alarm might cause someone to repeatedly search a room because they believe they are being watched but cannot find the source. More dangerously, failing to detect a real surveillance device could convince someone that an environment is safe when it isn’t.
These concerns can be especially serious for people experiencing domestic abuse, who may already be dealing with fear, uncertainty and heightened vigilance.
Based on their findings, the researchers proposed that spy-device detectors should be judged not only on technical accuracy but also on usability, clarity, verification support and emotional safety. Manufacturers should explain uncertainty clearly and help users determine what a detected signal actually represents.
However, the researchers stressed that no consumer detector is likely to find every hidden device.
Senior author Dr. Leonie Tanczer of UCL also called for greater scrutiny of covert surveillance products themselves. While many are sold as ordinary security products, she noted that cameras deliberately hidden inside everyday objects are specifically designed to avoid detection.
The study suggests that for people trying to protect themselves from secret surveillance, a detector alone should not be treated as proof that a room is safe.
