Bugs in your home: how to find a listening device and what to do next

A listening device can be planted in a home in ten minutes for about 40 dollars. A GSM bug the size of a matchbox plugs into a power strip or a power bank and calls the eavesdropper whenever it hears a voice. A WiFi camera fits inside a phone charger. The good news: every one of these devices leaves a trace, just a different one. This guide shows how to find a bug in your house with methods that work, and why some popular tips are useless.

What kind of bugs are planted in homes

Before you search, you need to know what you are looking for. The method depends on the type of device.

• GSM bug. Has a SIM card and transmits over the mobile network like a phone. The most common type, because it works from any distance. It only transmits when someone calls it or when it detects sound. Powered from a wall socket, a power strip, a USB charger or a built-in battery that lasts a few days.
• Radio transmitter (RF). Transmits continuously on a frequency between tens of MHz and a few GHz, with a range from tens to hundreds of meters. Cheaper and simpler than GSM, but the eavesdropper has to stay nearby with a receiver.
• WiFi device. An IP camera or microphone that connects to your router or to its own hotspot and streams to an app. The most convenient for the eavesdropper: live video and audio.
• Voice recorder. Transmits nothing. Records to a memory card for dozens of hours, and somebody has to come back for it. No signal detector will find it, only a physical search.
• Spyware on your phone (stalkerware). Not a device in the room, but the result is the same: someone hears your calls. You check it on the phone, not in the apartment.
• Bluetooth trackers (AirTag, SmartTag). They do not listen, they track. Your phone warns you about an unknown tracker that travels with you.

If your scenario is an office or a meeting room, read the separate guide: How to detect eavesdropping at work. For companies that want to check their premises systematically there is Counter-surveillance in business.

How to detect a bug with household methods: what works and what is a myth

What works:

1. A physical search with a checklist. Boring, but it is method number one. A bug has to be close to conversations and close to power. The list of places is below.
2. The device list in your router. Every WiFi camera or microphone connected to your network shows up in the router panel or in an app such as Fing. An unknown device named something like "IPC", "Cam" or "ESP", or made by a Shenzhen manufacturer, is a lead.
3. A lens finder. A camera must have an opening for its lens, even 1 mm wide. The reflection of the lens is visible in the detector's viewfinder from several meters away, including inside a plush toy or a smoke detector.
4. An RF detector. Finds transmitters that are transmitting right now: RF bugs always, GSM bugs during transmission, WiFi devices. It will not find a voice recorder or a GSM bug in standby.
5. A WiFi detector. Scans the 2.4 / 5 / 6 GHz bands and shows transmitting devices nearby, including ones connected to a stranger's hotspot that you will never see in your own router.

What is a myth or works poorly:

• "Make a call next to the suspicious spot and listen for crackling." GSM interference in speakers is a 2G-era phenomenon. Modern bugs work on LTE and nothing crackles.
• "Bug detector" apps that use the magnetometer. The magnetometer in a phone detects the magnet in a speaker or a motor, not a transmitter. Every cable in the wall gives a false alarm.
• Switching everything off and listening to the silence. Surveillance electronics do not beep. If they beeped, nobody would buy them.
• A flashlight on the lens "by eye". Works only in a dark room, with the flashlight next to your eye, from less than a meter and with a lot of patience. Better than nothing, but a lens finder does it in a minute.

How to find a bug in your house: the list of places to check

The person planting a bug picks a place by three criteria: close to conversations, close to power, out of sight. Check in this order:

1. Power strips, extension cords and USB chargers, especially new ones or ones "forgotten by a guest". The favourite housing for GSM bugs, because they have power forever.
2. Wall sockets and light switches. A loose frame, fresh scratches on the screws, a different shade of plastic.
3. Smoke detector, motion sensor, thermostat. Standard housings for pinhole cameras.
4. Lamps, clocks, alarm clocks, photo frames, speakers, plush toys, flower pots, curtain rails.
5. The underside of the table, the desk and the bedside tables. Nobody looks under the tabletop, and it is closest to conversations.
6. The car: under the seats, in the glove box, behind the bumper (GPS trackers), in the OBD port.
7. Things brought in from outside: a gift, a "borrowed" charger, a power bank, a cable.

Look for fresh dust, screwdriver marks, extra wires and 1-2 mm holes that have no reason to be there.

How to locate a bug in your home step by step

1. Do not discuss your suspicions in the room you suspect. If you are right, the eavesdropper hears it first.
2. Prepare: a flashlight, your phone in airplane mode, access to the router panel, a detector if you have one.
3. Scan the WiFi network. List every device in the router, check unknown ones by MAC address and name.
4. Go through the list of places above, starting with power strips. Photograph anything suspicious before you touch it.
5. Sweep the room with a lens finder, in a darkened room, slowly, at eye level and lower.
6. If you have an RF detector: switch off your own WiFi, Bluetooth and phones for the duration of the sweep. Walk the room slowly, along the walls and sockets. A signal that rises near one spot is a lead.
7. Check your phone: unknown apps with microphone permission, unusual battery and data use, alerts about unknown trackers.

A sweep like this takes 30-60 minutes. Do it twice: once now, again a week later. A GSM bug can stay silent on the first pass.

What to do when you find a bug

• Do not destroy it and do not throw it away. The device is evidence. Photograph it where it was, together with the surroundings.
• Do not touch it with bare hands if you can avoid it. There may be fingerprints on the housing.
• Report it to the police. Planting a bug or a camera to obtain information you are not entitled to is a crime in most countries; in Poland it is Art. 267 § 3 of the Penal Code, with up to 2 years in prison.
• Do not confront anyone right away. Think about who had access to the apartment and when.
• If the bug is tied to a divorce, an inheritance or a business dispute, talk to a lawyer before your next move.

Bug and camera detectors: which equipment to choose and when to call a professional

Search any shop and you will find hundreds of "bug detectors" from 15 dollars up. For a one-time check of an apartment you need two types of device:

• A lens and WiFi device detector. Finds cameras (even switched-off ones, because it looks for the lens) and everything transmitting in the WiFi bands. The simplest to use and the most unambiguous: either you see the reflection or you do not.
• A wideband RF detector. Catches radio and GSM transmitters while they are transmitting. In an apartment building with dozens of WiFi networks and phones behind the wall it gives many false alarms, so sweep with your own equipment switched off.

A professional sweep (TSCM) makes sense when the stakes are high: a court case, a trade secret, a suspected wired bug or one built into the installation. A specialist uses a spectrum analyzer, a non-linear junction detector and a thermal camera, and checks the cabling too. For a home or an apartment, the self-check described above finds most of the devices that actually get planted.

Frequently asked questions

How do I check if I have a bug in my house without equipment? Go through the list of places in this article and look at the device list in your router. That catches most GSM bugs in power strips and chargers and every camera connected to your WiFi. A lens finder does the rest.

Is there an app that detects bugs in the house? Apps using the magnetometer or an "EMF scanner" do not detect transmitters. Your phone is useful for two things that work: scanning the devices on the WiFi network (apps such as Fing) and alerts about unknown Bluetooth trackers.

How do I find a camera with a microphone? Every WiFi camera sold online has a microphone. You look for it like a camera: a lens from 1 mm in a flashlight beam or with a lens finder, and an entry in the WiFi device list. Separate guide: How to find hidden cameras in an apartment, hotel or Airbnb.

What does a bug look like? Usually like something else: a charger, a power strip, a smoke detector, a clock. The device itself is a coin-sized board with a SIM card or a WiFi module.

Does a bug work without power? From a battery, a few days to a few weeks, then it goes silent. That is why bugs are planted in things with power.

How often should I check my home? After every situation where a stranger had unsupervised access: renovation, repairs, renting, a conflict with someone who has keys.