Reports are flooding that many, but not all, Tumblr accounts have been attacked and hacked by a group calling itself the GNAA - a deeply racist anti-blogging and internet trolling organisation. Not only does the spam posting that's appearing across personal accounts carry a worm virus, it is unremittingly offensive.
The group, known in full as the Gay Nigger Association of America, has previously trolled the campaign website of Barack Obama and numerous other US-based media organisations, but this is the first time it is responsible for such a large scale hack attack.
If you visit a Tumblr site with the following posting, do not click on any of the links. If you do, it will repost on to your own Tumblr feed and so on and so forth. Even some company Tumblr sites are being affected, such as those from US technology site The Verge.
"Yes, our Tumblr appears to have been hacked," it says on its Twitter feed. "We're taking care of this - and we recommend staying away from those nasty links."
There are even reports that trying to close the offending page/tab will transmit the virus, so it's best not to click on Tumblr links highlighted on Twitter or such like.
Buzzfeed.com has a recommendation for those affected. "If your blog becomes infected go to your blog's Mega-Editor and mass delete the posts. Also, change your password. The blast of messages usually only lasts 10 minutes or so," the site suggests.