Eavesdropping devices planted in your home or office can give your adversaries or competitors access to confidential information shared in private conversations. Since the detection and location of listening devices, or "bugs," is difficult, even for experts, an experienced professional should be hired to do the actual scan. However, if you feel that your privacy, in your home or office, has been compromised by listening devices installed by eavesdroppers, there are steps you can take, and warning signs to watch for, prior to hiring a professional.
Watch and listen for indications that others are privy to information thought to be confidential. If competitors or adversaries have a knowledge of private matters, you should question how they received this information.

Be aware of unauthorized and unrequested visits from technicians checking phone lines, heating and cooling units, computers or any other devices within your home or office. Eavesdroppers will often use this type of tactic to gain entry into the building to install listening devices.

Take any gifts you receive from suspicious contacts to a technical countermeasures specialist for investigation. Gifts ranging from electronics to pens and picture frames can house listening devices. Have the items checked before bringing them into any room where private conversations are held.
Examine the room for anything that seems out of place. This includes wall plates, exit signs, clocks, lamps or smoke detectors that are new, jarred, crooked or a different shade (signifying that they may have has been replaced.) Examine such items for small holes. Furniture and decor may also be slightly askew, giving the room a feeling of having been "burglarized" without anything being missing. Intruders are often unable to replace things exactly as they were, and you will often be able to detect the slightest movement of fixtures.

Examine floors for debris. Installing listening devices often involves moving ceiling tiles or lighting fixtures or drilling small holes in walls and ceiling tiles. Also, check ceiling tiles for any cracks or other damage as they are fragile and often damaged when being moved. To make this process easier, regularly examine and replace any chipped, cracked or otherwise damaged ceiling tiles, so you will be able to tell when something is different with them.

Watch for suspicious vehicles in the vicinity. Service trucks or vehicles with back areas, where someone can sit and monitor any listening devices, that appear for long hours and frequently should be suspect.

Listen for unusual sounds coming from your phone line or interference with televisions or radios within the room. Volume changes or static, popping and scratching noises on your phone line may be an indication of a listening device. If your phone makes sounds when it is on the hook, there is a probability of it being used as a listening device. If you find there is a squealing noise when tuning your AM/FM radio, slowly move the radio around the room. If the radio emits a very loud, high-pitched squeal, this is often feedback from a listening device.

Contact a professional to conduct a Technical Security Countermeasures (TSCM) survey, or sweep, of the area. Prior to the professional arriving, do not discuss the possibility of a listening device in the compromised room or on the phone. If the eavesdropper is aware that you are suspicious, he may take steps to make the listening device more difficult to locate.