I read a post, last month, on the PandaLabs blog about a version of ransomware they came across, and bookmarked it. They actually cracked the code and the valid serials for it are posted on the page. There's also a video showing you just how this thing goes about it's business, it's worth watching for anyone who's not seen one of these things in action. The fake program is called 'Adware/TotalSecurity/2009'.
The blog post is
here.
It's worth a read... pays to be vigilant.
deya