Facebook says that the spammer hit thousands of profiles before the company removed the spammy photos and notified affected users. No accounts were compromised as a result of the bug, Facebook said.

People whose Walls were hit with the spam got a notice from Facebook's security team, reading:

"For a few hours on Sunday, there was a spamming incident on Facebook. During this time, photos -- mostly of supposedly 'free' iPhones -- were posted to some people's Walls, including yours. We've removed the photo from your Wall and fixed the issue that allowed spammers to do this. We're sorry about the photo, but can assure you that this did not affect the security of your account in any way."

Spammers love Facebook because users are more likely to click on Facebook messages and wall posts than on links in unsolicited e-mail messages.

that allow users to see if unauthorized computers have been used to log into their accounts.