Why VOIP Needs Crypto

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.L33tdawg: For a chance to meet Bruce Schneier, make sure you mark your calendars for HITBSecConf2006 - Malaysia. Mr. Schneier will be delivering a keynote address at our 6th deep-knowledge network security conference. You don't want to miss this!