Security researchers detected hackers distributing software to break into computers using flaws announced last week in some versions of Microsoft Corp’s Windows operating system. The threat from this new vulnerability is similar to the one that allowed the Blaster virus to infect hundreds of thousands of computers recently. The discovery gives fresh impetus for Windows users to immediately apply a free repairing patch from Microsoft. Researchers from Idefense Inc of Virginia, who found the new attack software being distributed from a Chinese website, said it was already being used to break into vulnerable computers and implant eavesdropping programmes.