Hong Kong's Office of the Telecommunications Authority says it had received 13 055 reports of suspected contraventions up to the end of July and had sent out 89 warning letters.

But spam is an international problem and legislation can only be effective if countries work together, says Roy Ko, manager of the government-funded Hong Kong Computer Emergency Response Team Coordination Centre.

"These days we receive spam from around the world... They are being sent out from locations that haven't implemented anti-spam laws. Unless we have a group effort on fighting spam we will keep receiving spam mails."

Part of the problem, say experts, is that the cyber criminals are often one step ahead of the legislators.

"Botnets" are the new weapon of choice in the spam war. Short for "robot network" ? these are networks of zombie computers that, unknown to their owners, have been taken over by a remote controller to undertake all kinds of skullduggery.

Highly professional gangs are responsible for a vast majority of online crime ? now a 100 million-US dollar global industry. Gangs are a worldwide phenomenon and many operate from China, though not from Hong Kong itself.

"Botnets are fast becoming the air supply of the spammers," Paul Wood, a senior analyst at MessageLabs, told AFP.

"In 2008, botnets were responsible for as much as 90 percent of all spam." Wood estimates that there are around 4000 zombie computers active in Hong Kong, around 40 times higher than would normally be expected for a region of around seven million people.

Most experts advise people to filter out spam using the software that comes free with most internet email accounts.