According to new figures, the number of ‘spam’ messages has tripled since June and now accounts for as many as nine out of ten emails sent worldwide.

Despite efforts by government officials and computer firms to crack down on spam, spammers are sending out more junk email than ever, finding new ways to get past filters and other security measures.

US email security firm Postini has detected 7 billion spam emails worldwide in November, compared with 2.5 billion in June. In Britain spam has risen by 50% in the last two months alone.

Daniel Druker of Postini believes criminal gangs are behind the rise in spam volumes:

“This dramatic rise in spam attacks on corporate networks has the Internet under a state of siege.”

“Spammers are increasingly aggressive and sophisticated in their techniques, and protection from spam has become a front-burner issue again. Spam has evolved from a tool for nuisance hackers and annoying marketers to one for criminal enterprises.”

Spamhaus believes that around 200 million illegal gangs are behind the majority of spam, and blame the rise on software that hijacks millions of home computers to send emails.

These ‘botnets’ can link up to 100,000 home computers to send out a wave of spam without their owners’ knowledge. Gangs are now sending out fewer emails from each PC, which makes detection more difficult.

ISPs have previously come under criticism for failing to deal with the problem at its source, though some have started to introduce measures to deal with the problem.