brought down the world's largest spam network, Rustock.
Rustock, at its peak, was a botnet of around 2 million spam-sending zombies capable of sending out 30 billion spam email per day. Microsoft's wholesale slaughter of Rustock could reduce worldwide spam output by up to 39%.
Rustock was taken down, piece by piece, in a similar way to the Mega-D botnet. First the master controllers, the machines that send out commands to enslaved zombies, were identified. Microsoft quickly seized some of these machines located in the U.S. for further analysis, and worked with police in the Netherlands to disable some of the command structure outside of the U.S.