Cellular Phones Vulnerability to Monitoring

number by others to make calls that are charged to your account.

Before discussing these vulnerabilities, here is a brief tutorial on how cellular phones function. They send radio frequency transmissions through the air on two distinct channels, one for voice communications and the other for control signals. When a cellular telephone is first turned on, it emits a control signal that identifies itself to a cell site by broadcasting its mobile identification number (MIN) and electronic serial number (ESN), commonly known as the "pair."

When the cell site receives the pair signal, it determines if the requester is a legitimate registered user by comparing the requestor's pair to a cellular subscriber list. Once the cellular telephone's pair has been recognized, the cell site emits a control signal to permit the subscriber to place calls at will. This process, known as anonymous registration, is carried out each time the telephone is turned on or picked up by a new cell site.

Cellular Phones Vulnerability to Monitoring

All cellular telephones are basically radio transceivers. Your voice is transmitted through the air on radio waves. Radio waves are not directional -- they disperse in all directions so that anyone with the right kind of radio receiver can listen in.

Although the law provides penalties for the interception of cellular telephone calls, it is easily accomplished and impossible to detect. Radio hobbyists have web sites where they exchange cell phone numbers of "interesting" targets. Opportunistic hobbyists sometimes sell their best "finds." Criminal syndicates in several major U.S. metropolitan areas maintain extensive cell phone monitoring operations.

Cell phones operate on radio frequencies that can be monitored by commonly available radio frequency scanners.

If the cellular system uses analog technology, one can program a phone number, or a watch list of phone numbers, into a cell-monitoring device that automatically turns on a voice-activated tape recorder whenever one of the watch listed numbers is in use. Computer assisted, automatic monitoring allows monitoring a specific phone 24 hours a day, as the target moves from cell to cell, without any human assistance.

If the cellular system uses newer digital technology, it is possible for a price affordable by most radio hobbyists to buy a digital data interpreter that connects between a scanner radio and a personal computer. The digital data interpreter reads all the digital data transmitted between the cellular site and the cellular phone and feeds this information into the computer. 

It is easy for an eavesdropper to determine a target's cellular phone number, because transmissions are going back and forth to the cellular site whenever the cell phone has battery power and is able to receive a call. For a car phone, this generally happens as soon as the ignition is turned on. Therefore, the eavesdropper simply waits for the target to leave his or her home or office and start the car. The initial transmission to the cellular site to register the active system is picked up immediately by the scanner, and the number can be entered automatically into a file of numbers for continuous monitoring.

One of the most highly publicized cases of cellular phone monitoring concerned former Speaker of the House of Representatives Newt Gingrich. A conference call between Gingrich and other Republican leaders was "accidentally" overheard and then taped. The conversation concerned Republican strategy for responding to Speaker Gingrich's pending admission of ethics violations being investigated by the House Ethics Committee.

The intercepted conversation was reported in the New York Times and other newspapers.

Pagers have similar vulnerabilities. In 1997, police arrested officials of a small New Jersey company, Breaking News Network, that was monitoring pager messages to New York City leaders and police, fire, and court officials, including messages considered too sensitive to send over the police radio. They were selling the information to newspaper and television reporters. The offenses carry a penalty of up to five years in prison and fines of $250,000 for each offense.

Source :http://www.hq.nasa.gov/office/ospp/securityguide/V2comint/Cellular.htm