Officials at Facebook are warning that a of rash of pornographic and graphically violent images has been flooding the popular social network over the last few days. They are urging the site's millions of members to be cautious.

The images, according to various reports, range from doctored photos of celebrities in compromising positions to pictures of dead animals.

Security experts believe that the rapid spread of these images may be due to "click-jacking"—an attack that uses a link to a seemingly innocuous story as bait. Once clicked on an unsuspecting Facebook user's wall, the link actually posts the illicit images and link to the walls of the user's list of Facebook friends, thus spreading the virus.

Some online-security firms believe the hacking group know as Anonymous may be responsible for the flurry of graphic images. A Facebook spokesman told Fox News online that the company is "investigating and addressing the issue. Protecting the people who use Facebook from spam and malicious content is a top priority for us."

Consumer Reports online experts urge Facebook users to be extremely cautious. In particular, do not click on any public links on Facebook that you are unsure of—even if they are supposedly posted by your online friends.

For more online safety tips, including the 7 things you should stop doing on Facebook, see Consumer Reports guide to online security.

Clickjack attacks plaguing Facebook with 4chan-like porn, violent imagery [Ars Technica]
Facebook 'virus' shows hardcore porn and violent images [BBC News}
Facebook Flooded With Porn and Violent Images, Company Warns [Fox News]