Some enterprising hackers put up what was ostensibly an image viewer on various sex sites.
In actuality, the program turns off your PC's modem speaker, disconnects you from your ISP, and dials a number in Moldova which then connects
to a server in Canada. The victim happily surfs scantily clad bipeds while racking up hundreds of dollars in long distance charges. Charges keep
mounting after leaving the sex site, because the victim's still connected to the Internet via Moldova and Canada.
Watch out for files called david.exe and david7.exe and expect to see more trojan horse programs that play around with your modem behind your back.
The New York Times has an excellent article in their CyberTimes section -
http://www.nytimes.com/library/cyber/week/021197scam.html