Spying devices are tools used to secretly observe or listen to conversations and activities. The most common spying device is a BUG, which is a small electronic device that can be hidden in an object or room to record audio or video. A WIRE is another type of spying device, which is a device that is placed on a person to record their conversations. DISGUISE is also a form of spying device, which is used to conceal the identity of the person using it. All of these devices are used to gain information without the knowledge of the person being spied on.