It may be Microsoft’s time to feel a little smug. For years Redmond has been the butt of jokes — and curses — for the vulnerability its systems seemed to have to viruses. Now Linux has fallen prey to a nasty bug of its own, one that has created a giant peer-to-peer attack network from thousands of infected Linux Web servers. Only computer systems running both Apache Web server software and the Linux operating system are vulnerable, New Scientist reports. But that’s a heck of a lot of machines. Once installed on a machine, the Linux.Slapper.Worm tries to forward itself on to other computers. “But unlike many other worms, it also tries to establish connections with computers that have already been infected,” the magazine reports. The bug was first identified Friday, and though characterized by computer security firms as slow-moving, has so far infected an estimated 3,500 machines. In a note accompanying the worm, the author says it was designed as a proof-of-concept for “educational” purposes and should not be used for destructive attacks.