Bugbear disables millions of PCs across the globe

Since then it has spread worldwide, affecting millions of computers in Europe, the US and Asia.

Bugbear is being considered more powerful than Klez virus, which has been plaguing computer users since February. It is what security experts call a ‘‘blended threat,’’ carrying out multiple attacks once inside a computer.

It records users’ keystrokes to capture passwords or credit card numbers and attaches itself to e-mails.

The virus also disables anti-virus and firewall programmes designed to protect computers from attack and can install a ‘‘trojan’’ that will allow hackers remote access. The virus is difficult to spot as the e-mail has more than 50 different catch lines.

One way of identifying it is looking at the size of the file attachment, which is usually 50,688 bytes, but some copies have been different sizes.

Bugbear can delete some anti-virus software, and also enables people to add or delete computer files.