Key Points:

Two years ago police moved in to arrest 61 Australians in a swoop on a new crime plague sweeping the world - "money mules", work-from-home, part-time crooks using their computers to launder tens of millions of dollars daily.

The Australian mules earned between A$200 ($227) and A$500 for moving up to A$100,000 of laundered cash a day, mostly for crime gangs based in Russia.

They were far from alone.

The Australian Institute of Criminology says three Britons used 13 bank accounts to rob eBay customers and launder the proceeds, and last year Russian thieves stole more than €1 million ($1.85 million) from personal bank accounts in France and used mules to shift it.

And in Spain last September, police detained 23 people in relation to the theft of €2 million from online banks and shops, which was then transferred to Russia and Ukraine by 19 mules.

It is, the institute warns in a high-tech crime brief, a rapidly-expanding headache for law agencies.

One estimate said that between September and October 2005, work-at-home scams had soared from 0.5 per cent of all spam emails to 1.2 per cent, while another report said that more than 20,000 copies of a mule recruiting email were distributed using the name of a legitimate company, ICG Commerce, to gain credibility.

The Western Australian Consumer and Employment Protection Department said more than 1700 employment and money mule emails were reported by consumers in October last year alone - 59 per cent of all scam emails.

And unlike other work-at-home schemes offered over the internet, money-muling can put its part-time workforce behind bars for money laundering.

The institute says gangs use simple methods to recruit mules to transfer relatively small amounts of illicit money lodged in their bank accounts to criminals overseas, mainly in the countries of the former Soviet union.

Together, the flow of money from numerous small transfers adds up to millions of dollars.

The gangs find mules by offering work as "financial agents" or similar titles through spam emails.

When they accept the job, the mules open - or allow access to - domestic bank accounts.

The gangs transfer money from scam victims to these accounts, and the mules transfer the money to an account overseas in exchange for a "commission".

The institute says the work is usually offered through cyber fronts - fake but apparently legitimate online companies - or emailed spam advertisements.

Unlike phishing scams - in which victims have no idea their accounts have been compromised - the mules give gangs their full consent and co-operation, potentially exposing themselves to criminal charges.

Most are recruited in Australia, the United States, and Britain.

The institute says international crime gangs also use a variation called reshipping, under which mules are sent stolen goods through the mail for forwarding, in exchange for a fixed fee.

The fee is usually paid directly into the mule's account.