ITWire

Microsoft, which launched the free Security Essentials package for Windows in late September in eight major markets, revealed the figure as it prepares to roll out the software in China.

"What we're seeing in the early downloads is that well over 30% of people who are downloading it are requiring a fair amount of cleaning," said Amy Barzdukas, general manager, Internet Explorer and consumer security at Microsoft.

Delivering the opening keynote at RSA Conference Europe in London, Barzdukas also noted that the problems experienced by consumers varied widely by area.

"In China, we see a lot of malicious browser modifiers. In Brazil, there's a lot of password stealers. In Korea, there's a lot of polymorphous viruses. There's no one size fits all in consumer security any more than in enterprise security."

Microsoft's move into the consumer security space has been controversial, with critics variously arguing that Microsoft will reduce competition in the security sector and that it should concentrate on making its core operating system more secure. However, Barzdukas said that Windows itself was only a small part of the problem.

"Fewer than 15% of the vulnerabilities that are being exploited today are in the browser or the OS. Instead they're going into third party software and add-ons."

Barzdukas also took a pot shot at Google's rival browser Chrome, claiming that features of its design made it less secure than Internet Explorer 8.

"As you type in that omnibox, every keystroke that you type is sending a packet to Google."