Microsoft, working with law enforcement agencies and industry partners, has taken down the Waledac botnet, believed to be one of the biggest in the world.

The company is hailing the operation as a victory in its fight against botnets.
"Botnets – networks of compromised computers controlled by hackers known as “bot-herders” – have become a serious problem in cyberspace," states the official Microsoft blog. "Their proliferation has led some to worry that the botnet problem is unsolvable.
"Under the control of a hacker or group of hackers, botnets are often used to conduct various attacks ranging from denial of service attacks on websites, to spamming, click fraud, and distribution of new forms of malicious software.
"At Microsoft, we don’t accept the idea that botnets are a fact of life," it adds.
Microsoft is a founding member of the Botnet Task Force, a public-private partnership to join industry and government in the fight against bots. This week the task force succeeded in bringing down the Waledac botnet.
"The takedown of Waledac – known internally as “Operation b49” – was the result of months of investigation and the innovative application of a tried and true legal strategy," the blog states.
"One of the 10 largest botnets in the US and a major distributor of spam globally, Waledac is estimated to have infected hundreds of thousands of computers around the world and, prior to this action, was believed to have the capacity to send over 1,5-billion spam emails per day. "
In a recent analysis, Microsoft found that between 3 and 21 December 2009, approximately 651-million spam emails attributable to Waledac were directed to Hotmail accounts alone, including offers and scams related to online pharmacies, imitation goods, jobs, penny stocks and more.
On February 22, in response to a complaint filed by Microsoft, a federal judge granted a temporary restraining order cutting off 277 Internet domains believed to be run by criminals as the Waledac bot.
This action has effectively cut off traffic to Waledac at the “.com” or domain registry level, severing the connection between the command and control centres of the botnet and most of its thousands of zombie computers around the world.