There are basically four ways to eavesdrop on a telephone call. One, you can listen in on another phone extension. This is the method preferred by siblings everywhere. If you have the right access, it´s the easiest. While it doesn´t work for cell phones, cordless phones are vulnerable to a variant of this attack: A radio receiver set to the right frequency can act as another extension.
Two, you can attach some eavesdropping equipment to the wire with a pair of alligator clips. It takes some expertise, but you can do it anywhere along the phone line´s path — even outside the home. This used to be the way the police eavesdropped on your phone line. These days it´s probably most often used by criminals. This method doesn´t work for cell phones, either.
Three, you can eavesdrop at the telephone switch. Modern phone equipment includes the ability for someone to listen in this way. Currently, this is the preferred police method. It works for both land lines and cell phones. You need the right access, but if you can get it, this is probably the most comfortable way to eavesdrop on a particular person.Read Full Story