Summary Box: Facebook warns of recent wave of spam

UNDER CONTROL: Facebook says it has stopped most of the spam that has flooded many users’ pages in recent days with pictures showing graphic sex and violence.

USER VIGILANCE: Users are encouraged to report suspicious links on friends’ pages and avoid clicking on links that offer deals that are too good to be true.

WHY THIS SPREADS: Social-networking sites are popular targets for spammers because people are more likely to trust and share content that comes from people they know. Still, Facebook says less than 4 percent of content shared on the site is spam.