This is usually caused by a drive-by as McKenzie said. But if it came as a piggy back on AIM D/L I would contact them to notify that it is on their website. If this is happening many people are being infected.
The Federal Trade Commission has issued a statement saying that you do not have to pay your local telephone company for these charges, regardless of what they say. You should "refuse to pay for anything you did not authorize, as long as it's not a transmission charge," FTC officials said. The reason being, charges for hijacked calls to XXX Web sites count as charges for content not transmission. Follow the steps below under "What to do" for more help.
Here's how it works...
1) The consumer - usually a teenager - logs on to a computer and accesses a pornography site through his or her Internet Service Provider (ISP).
2) A teaser Web site then downloads "dialer" software onto the consumer's computer.
3) After "dialer" software is activated, the consumer's computer modem disconnects from the ISP and dials an international telephone number assigned to Madagascar, Vanatu or another distant foreign country.
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http://clarkhoward.com/topics/porn_charges.html#todoMore Help Here:
FREE Malicious Software Removal Tool from Microsoft
http://www.xpmaximized.com/archives/2005/01/malicious_softw.htmlSecurity Tools
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=242x1314