A computer presents very little risk if it's by itself. The problem arises when it's hooked up to a modem. A modem is a communications device that allows your computer to talk with another computer. Modem is short for modulator/demodulator. It is, basically, a telephone for your computer. It converts the computer's output to a format that can be sent over telephone lines.

If your computer has a modem connected to the Internet, it is like you are living in a high-crime neighborhood. You must take appropriate precautions. The modem connection can be a significant vulnerability. Any unauthorized modem is a serious security concern.

Hackers commonly use a tool known as a "war-dialer" to identify the modems at a target organization. A war-dialer is a computer program that automatically dials phone numbers within a specified range of numbers. Most organizations have a