Microsoft legal action

Security experts are split over the effectiveness of Microsoft's efforts to shut down a network of computers that spewed out 1.5 billion spam messages.

The firm persuaded a US judge to issue a court order to cripple 277 internet domains used by the Waledac botnet.

Botnets are armies of infected computers that send spam or malware.

"We aim to be more proactive in going after botnets to help protect the internet," said Richard Boscovich, the head of Microsoft's digital crime unit.

"We will do whatever it takes to look out for our customers and our brand. We hope it will spur similar actions," Mr Boscovich told the BBC.