A false-positive glitch occured on the McAfee VirusScan software. The article at The Register mentions that the customers include those who live in Germany and Italy.

A UK-based user sent a message to the website and notes that half of a customer’s 140 machines are affected. “Literally half of the machines were down with this McAfee anti-virus message IDing valid programs as having this trojan. Literally half the office switched off their PCs and were just twiddling their thumbs,” he said.

The program indentified winvnc.exe and other legitimate files as malware.

Source: The Register