Ads to blame for malware in Facebook's Farm Town?

The 9.6 million players of the Facebook game Farm Town are being warned about fake security warnings popping up that are designed to mislead people into paying for antivirus protection they don't need.

"We are aware and have reported to the developers that many of our players have encountered the malware/spyware while on the Farm Town site," the moderator of a user forum for Farm Town maker SlashKey warned over the weekend. "We believe at this time that it is harmless to your computer and a result of one or more of the ads on the site, but you should NOT follow any links to any software claiming to 'clean your system.'"

Sophos' Graham Cluley said it appeared that third-party advertising displayed underneath the Farm Town playing window is to blame.

"In all likelihood, hackers have managed to poison some of the adverts that are being served to Farm Town by the outside advert provider," Cluley wrote on his blog. "Rather than SlashKey simply asking its players to report offending adverts when they appear, it might be sensible for the company to disable third-party adverts appearing alongside Farm Town until the problem is fixed."

SlashKey could not be reached for comment on Monday. Farm Town competes on Facebook with FarmVille, which has 86.6 million users and critics of its own.

Malware has been found in ads delivered by Yahoo, Google, and Fox ad platforms, as well as on high profile sites like The New York Times and the Drudge Report.

Last week, Facebook was hit with another scam involving a fake Ikea gift card offer. Nearly 40,000 Facebook users signed up for a $1,000 Ikea gift card offer and joined a related Facebook fan page and were duped into providing personal information on an outside Web site including birth date and home phone number, according to IDG News Service. The latest scam follows a similar Ikea gift card ripoff and a $500 Whole Foods gift certificate on Facebook.

A Facebook spokesman said the company is trying to head off such scams by researching specific dubious groups and pages and developing technical systems to surface them more quickly.

"We advise people to be suspicious of anything that looks or feels strange online--whether it's an unfamiliar link in a message from a friend who hasn't contacted you in a while, or a promise of something valuable if you take a certain action or provide personal information," Facebook said in a statement. "It's a good idea to also check with the retailer whose gift cards are being offered to verify that the offer is legitimate. Be wary of groups and pages that don't appear to be the retailer's official Facebook presence, as well as those whose only purpose is to promote the offer (for example, those that have the offer in their names)."