On Wednesday, at the RSA Conference 2010 in London, Microsoft revealed that it had cured 6.5 million botnet-infected computers during the second quarter of 2010, twice the number identified and removed during the same period in 2009.

Microsoft has identified 2.2 million computers compromised by botnet malware in the U.S. during the second quarter of this year. This is four times more than in Brazil, where 550,000 botnet infections were identified.

South Korea, who came in fourth of the overall infection count, emerged as the country with the highest density of botnet infections, with 14.6 per thousand machines scanned by Microsoft.

This news comes just days after the controversial blog post from Scott Charney, proposing that infected PCs should be quarantined.

Charney, Microsoft’s corporate vice president for trustworthy computing, proposed applying the public health model to computer security. Under such management, computers would have to prove that they’re sufficiently free of infection to connect to networks.

Whether or not this somewhat controversial proposal goes ahead, the record number of security breaches prevented by Microsoft this quarter, highlights that the software giant remains at the top of its game and is continually improving and innovating to improveglobal PC security.