Rustock - the world's biggest source of spam emails has been shut down after a series of raids by Microsoft and US Federal authorities. Rustock botnet is an international network of virus infected computers. It has generated billions of daily spam emails promoting unlicensed online pharmacies and cut price impotence pills. However, now Microsoft is quite successful in collapsing Rustock's operations. There was a court order that backed Microsoft in seizing the servers that were controlling almost a million Windows PCs. The servers were rented from commercial internet hosting firms in the Mid West but they were not aware of Rustock's spam operations. These command and control servers used to issue instructions to infected home and business PCs globally.