Citadel malware is reported to have infected machines in US, Europe and Hong Kong.
Microsoft said it has redeemed about two million PCs from Citadel botnet, which is reportedly unleashed to steal $500m from bank accounts worldwide.
Microsoft assistant general counsel of digital crimes unit Richard Domingues Boscovich was quoted by Reuters as saying that: "We definitely have liberated at least 2 million PCs globally. That is a conservative estimate."
He said the vast majority of infected machines were in the US, Europe and Hong Kong.
"We feel confident that we really got most of the ones that we were after. It was a very, very successful disruptive action," he said.
Reuters reported that the citadels ringleader, known as Aquabox, and dozens of botnet operators remain at large and the authorities are working to reveal their identities.
Earlier this month, it was revealed that Microsoft, the FBI and members of the financial services industry have disrupted more than a thousand botnets.
Microsoft has filed a civil suit against cybercriminals operating the botnet scheme, and received the approval of the US District Court for the Western District of North Carolina to cut off communication between 1,462 Citadel botnets and infected computers under their control.