Flawed software code used by numerous Microsoft applications to render images mean that a specially constructed image file could hijack a computer or spread a virus.
Ten years ago the idea of an image infecting a computer was the subject of a hoax email. But what was once a myth is now a genuine threat after Microsoft disclosed a flaw in the image processing code used in a range of its software programs on Tuesday.
Some experts blame the new threat on shoddy programming. "In a properly coded world, a graphic should not be able to infect your computer," says Graham Cluley, senior researcher with the UK-based anti-virus firm Sophos. "It should be impossible