Scammers are actively exploiting a bug in Firefox that causes the browser to lock up after displaying a message warning the computer is running a pirated version of Windows that has been hacked.

The message, which appears without any user interaction upon visiting a site, reads:

Please stop and do not close the PC… The registry key of your computer is locked. Why did we block your computer? The Windows registry key is illegal. The Windows desktop is using pirated software. The Window desktop sends viruses over the Internet. This Windows desktop is hacked. We block this computer for your safety.

Read full article on Technology Lab – Ars Technica