The four, prosecuted in Valladolid, in north-east Spain, had been recruited via 'work at home' schemes that often appear in spam inboxes and are widely advertised online.
Phillip Hallam-Baker, principal scientist at identification authority Verisign suggested that these schemes are re-shipping scams used to commit internet fraud.
"When you reply to an advert in an email or online you become a mule for the online organised crime heads," said Hallam-Baker. "They use the recruitment of large numbers of people, who often aren't sure they're committing a crime initially, to scale-up their operation."
The four stand accused of taking jobs in 'international money transfer,' schemes. According to the Spanish ABC website the scheme involved sending out spam phishing emails.
Hallam-Baker suggested such employment schemes represented the next phase in the evolution of online crime. Even traditional 419 scams, he suggested have moved on.
"There's certainly evidence to suggest that 419ers are now franchising their operations, promising huge money-making possibilities for those who take it up," he said. "It explains why so many are falling for the anti-419 website that show pictures of people holding fish, wearing silly hats and doing all manner of things to steal poeple's money."
Last month, SC Magazine reported on how 419 scammers work and the lengths they will go to in order to extract money from unsuspecting users.