A major malware botnet has sprung to life and is making a huge spam run through social networking sites.

Researchers at Symantec's MessageLabs branch said that the DonBot network has begun sending spam emails in large numbers, accounting for as much as four per cent of the total global spam load since 18 November.

The messages advertise a 'work at home' programme which promises $300 (£180) a day for posting information online.

"The apparent aim of these emails is to get people to fall for 'get rich by working at home' schemes where the victim is encouraged to pay an initial fee for a trial and then sit back and watch the cash come in," wrote Symantec malware analyst Paul Wood in a blog post.

Clicking on the spam image sends victims to one of any number of Twitter pages which contain links to a third-party site which asks the user to pay the 'trial fee'.

Researchers believe that the operation uses hijacked and specially created spam accounts on Twitter. Some hijacked Facebook pages are also being used to spread the links.

Social networking sites have become a favourite tool for scammers and malware writers of late. Attackers have used sites such as Facebook and Twitter to spread spam and infect new users.