Brad Pitt, Mariah Carey and George Clooney are among the stars whose names are being most exploited across the Web to lure unwary fans into downloading wallpaper and screensaver software that’s really malware in disguise.

McAfee this week issued a list of the 15 celebrity names it found to be most abused by those peddling crimeware. The most surprising omission: Paris Hilton, last year’s No. 1 most hijacked celebrity name.

“It’s completely disappeared,” says Shane Keats, research analyst at McAfee, which is at a loss to explain exactly why.

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The connection between celebrity names and malware across the Web is extreme, says Keats, noting that 18% of the Web sites discovered associated with the name Brad Pitt were found to have some sort of malware associated with them. “That’s high, when you consider that as a whole, about 4% to 5% of Web sites are risky across the entire Web.

“The bad guys follow the crowds and they’re interested in making a buck off off stealing your identity,” says Keats. It’s better to stick with well-known sites that focus on celebrity news, such as Entertainment Weekly, as the safest way to follow celebrity happenings, he notes.

As far as the celebrity names that have been most abused and exploited this year to create dangerous Web sites, malware downloads and spam, the top three names, according to McAfee, are:

1. Brad Pitt. When “Brad Pitt screensavers” was searched, more than half of the reporting Web sites were identified as containing malicious downloads with spyware, adware and potential viruses, according to McAfee.

2. Beyonce. Inputting “Beyonce ringtones” into a search engine yields risky Web sites that promote misleading offers to gather consumers’ personal information, according to McAfee.

3. Justin Timberlake. Spammer and hackers exploit interest in his high-profile relationships, and a search for “Justin Timberlake downloads” was flagged as leading to spam, spyware and adware.

The dozen other most-exploited celebrity names and combinations thereof are Heidi Montag, Mariah Carey, Jessica Alba, Lindsay Lohan, Cameron Diaz, George Clooney, Rihanna, Angelina Jolie, Fergie, David Beckham, Katie Holmes and Katherine Heigl.