Web criminals fuel rise in 'trojans'

Cyber-criminals are behind a dramatic rise in stealthy programs called "trojans" that infect computers to sell rogue software, send unwanted email or steal personal data, a study has found.

In a report released in London, Microsoft said the number of trojans removed from computers around the world in the second half of 2007 rose by 300 percent from the first half.

The figure has risen so sharply because more computers are fitted with software that detects malicious programs and because criminals had come to see trojans as their "tool of choice", the report said.