The FBI Ransomware Virus is Spreading and there are reports that there is no way to prevent it and once it is installed, which can be through visiting a website, or clicking on an attachment your computer may have been infected, and you may not see any sign of it, until you perform a system update, Microsoft, Symantec, Adobe all appear to be possible triggers of the virus.

So use extreme caution when you are on the web and especially when opening attachments from people you really don’t know.

There’s a few resources for dealing with the infection.
Botcrawl.com has a post here.