Are you noticing any pornographic or violent imagery on your Facebook news feed this morning? According to security firm Sophos, the social-networking site has been awash in objectionable material over the past 24 hours.
"Explicit and violent images have flooded the newsfeeds of many Facebook users in the last 24 hours or so," security consultant Graham Cluley wrote in a blog post. "The content, which includes explicit hardcore porn images, photoshopped photos of celebrities such as Justin Bieber in sexual situations, pictures of extreme violence and even a photograph of an abused dog, have been distributed via the site—seemingly without the knowledge of users."
As Cluley noted, offended Facebook users have taken to Twitter to vent their frustrations, with some saying they will deactivate their Facebook accounts.
Facebook confirmed that it had been hit with "a coordinated spam attack that exploited a browser vulnerability."
"Our efforts have drastically limited the damage caused by this attack, and we are now in the process of investigating to identify those responsible," a Facebook spokesman said.
The social-networking site said users were "tricked into pasting and executing malicious javascript in their browser URL bar causing them to unknowingly share this offensive content." Engineers have since built "enforcement mechanisms" to shut down the offending Pages, as well as accounts that exploit the vulnerability, Facebook said.
"We have also been putting those affected through educational checkpoints so they know how to protect themselves," the company continued. "We've put in place backend measures to reduce the rate of these attacks and will continue to iterate on our defenses to find new ways to protect people."
As Sophos pointed out, there was talk that the hack was related to Anonymous, "but that is unconfirmed." In a YouTube video (below) uploaded on Nov. 10, Anonymous said Facebook had been struck by the "Fawkes Virus," which "sends out malicious links and gains access to your account." The video likened the virus to Koobface, a virus that hit Facebook in 2008, and the voiceover said Anonymous would use the Fawkes Virus to tackle corruption and groups that oppose its organization. The video, however, did not discuss pornographic or violent images.
Of the various issues the incident brings up, Cluley pointed to companies that allow Facebook access at work. "What happens when hardcore pornographic and offensive content is being spread?" he asked. "Should companies block access to sites hosting offensive content?"
The firm also discussed a September incident that involved pornographic movies appearing on Facebook users' walls. "At the time we found no evidence of this occurring, and so considered the story likely to be a hoax," Sophos said. "In light of the most recent incident described below, it seems sensible to retract that advice."
Editor's Note: This story was updated at 4:30pm Eastern with more details from Facebook.