A Microsoft team in cooperation with the US Federal agents have taken down a major botnet, which was one of the largest out there: Rustock. Spam stopped from the botnet for quite a while, but it is probably only temporary.
The raiders brought a copy of the federal order allowing Microsoft to seize computers thought to have been taken over by the spam network, and that were relaying instructions to a million or more computers in the U.S. and elsewhere. Hard drives and computers were seized in the raids at the hosting providers. Much of the equipment had been leased by companies in other countries, according to Microsoft.