A worm called Conficker has recently been circulating. It uses infected PCs to spread. So far, around 2.5 million computers have been infected. Due to its ability to generate new code, it has not yet been possible to render the worm harmless.
"Conficker" uses a known security vulnerability in Windows to infect the computer. If you use the automatic update function of Windows, the corresponding security update has already been installed. To reliably remove the worm, Microsoft has updated the "Malicious Software Removal Tool" (MSRT).