Only more global co-operation will help stop the scourge of spam, say experts.
Spammers tried to cash in on the 9/11 attacks
At a conference called to debate anti-spam measures, US and UK government bodies said they had to work more closely to stop spammers.
Most spam originated overseas, so cross-border co-operation was essential to combat spam, delegates were told.
Without teamwork spammers would flourish behind a "cloak of anonymity" and perhaps do real damage to proper e-commerce, the conference was warned.
In 2001 only 10% of e-mail sent was spam but now almost 60% of all mails are junk, according to figures presented at the International Spam Enforcement Workshop held this week and organised by the US Federal Trade Commission (FTC) and the UK's Office of Fair Trading (OFT).
More than 20 nations sent representatives to the workshop, one of the first of its kind.
Almost 80% of junk mail originates outside the country where people receive it, making the tracing of who is sending the messages the biggest problem facing anti-spam efforts. speakers told delegates.
"Spammers hide behind the cloak of anonymity provided by the latest technology and the path from a spammer to a consumer's inbox typically crosses one border, if not several," said Deborah Majoras, chairwoman of the FTC.
Be aware that most spam is a scam
If an offer looks too good to be true, it probably is
If an e-mail looks doubtful, delete it
Use a spam filter
Avoid clicking on adverts in spam messages, they could download a virus
Protect your e-mail address. Do not share it with people you do not know.
Ms Majoras said tracing the origins of spam was the biggest problem and called for more sharing of information to help track down spam gangs.
John Vickers, OFT chairman, said spam was more than just a nuisance as statistics show that more than half of it is now produced by scammers keen to con people out of cash or useful personal information.
Many so-called phishing attempts that try to trick people into handing over account information are sent as e-mail messages.
"Spam is threatening the enormous potential for good that e-commerce, and the web generally, has opened up," said Mr Vickers.
Successful joint operations mounted by UK and US authorities include the shutting down of an operation sending spam that tried to cash in on the 9/11 attacks and sell people net domains.
Richard Thomas, the UK's Information Commissioner, said new powers were needed to help gather intelligence on spammers.
He said that currently net service firms were not obliged to hand over information about spam sent via their systems.
Mr Thomas called for powers to compel net firms to hand over data and to get injunctions fast-tracked, so spammers could be taken to court and tackled quickly.