I hope you haven’t noticed, but what’s apparently an attack on Facebook reportedly went viral last night. The “flood of violent and pornographic images invading [Facebook users’] news feeds” has prompted Facebook to launch an investigation, the Washington Post reports. The Post cites the view from security firm Sophos that “users whose accounts post the images are unable to see them on their own news feeds,” so your FB could be part of the problem without your knowing it. Theories on what’s happening include that it’s a scam “in which users click a link and open up their accounts to viruses that can post whatever hackers want to users’ profiles” and that “a splinter group of Anonymous made good on its threat to put out a virus to ‘take down Facebook,’ in an attack planned for Guy Fawkes Day, Nov. 5,” except the Post says there’s no evidence of Anonymous having taken credit. Here’s a Wall Street Journal blog post on this development.