A critical weakness found in many Microsoft programs looks like it is about to be exploited by virus writers.
The bug only came to light last week, but code is now circulating that could be used to attack vulnerable machines.
Some security experts said conditions were right to turn the bug into a widely exploited problem. But others said there was still time to patch machines and ensure that virus writers were prevented from scoring a big success.
Recommended: Click here to Update all your outdated drivers