Expensive dialing via viruses

There are some viruses, often intentionally downloaded by users as “good” programs that will try to force your modem to dial a premium, VERY EXPENSIVE PER MINUTE OR FLAT RATE CHARGES, telephone number.
So warning, when your modem dials be careful to know WHERE it’s dialing.
Also some of these programs will silently dial your modem so you never know it’s dialing! (full story)