Self-replicating golden rings called grey goo were appeared  in the air and on the ground at Second life. When people touched them, the ring copied themselves, they make horrible lags and infest 2700+ servers run by Linden Labs in California. Over 600 thousand users were influenced by the virus Linden Labs had to allow only their staff to login the game to clean the virus, grey goo.

[via blog.secondlife.com]