10. Bait, Switch, and Infect Ads
A related type of online ad is the kind that entices you with too-good-to-be-true offers. Such messages predate the Web, of course, but online they cause a lot of grief, notes Paul Piccard, director of threat research at Webroot Software.
Earlier this month the Web site of the Arizona Daily Star in Tuscon was hit with a "maliciously coded online advertisement," according to the newspaper's own report. The Star reports that the online ad was purchased by a company using a fraudulent credit card. The ad appeared on the newspaper's site for 18 days and "directed some Web visitors to sites that could have installed harmful software," says the Star's report.
Piccard says that such ads typically promote free software or another giveaway, trying to drive traffic to a booby-trapped Web page. If you click on such an ad, it whisks you away to a Web site that attempts to install malware onto your system through Web browser security holes.
As the Arizona Daily Star will attest, these ads can make their way onto legitimate sites and cause havoc. Piccard says that the malicious payloads these ads deliver to PCs include keyloggers (which collect and send personal identifying financial information), adware, and spyware.