A stealthy Windows virus

In the last month, the malicious program has racked up about 5,000 victims - most of whom are in Europe.

Many are falling victim via booby-trapped websites that use vulnerabilities in Microsoft's browser to install the attack code.

Experts say the virus is dangerous because it buries itself deep inside Windows to avoid detection.

The malicious program is a type of virus known as a rootkit and it tries to overwrite part of a computer's hard drive called the Master Boot Record (MBR).

This is where a computer looks when it is switched on for information about the operating system it will be running.

"If you can control the MBR, you can control the operating system and therefore the computer it resides on," wrote Elia Florio on security company Symantec's blog.

-Warning on stealthy Windows virus