Four people have pleaded guilty to involvement in a cybercrime ring, while another has had his plea deferred.
Teenager Nicholas Webber pleaded guilty at Southwark Crown Court on Friday to being involved in the management of a crime forum called Ghostmarket.net, which traded in stolen credit card details.
Ryan Thomas, another teenager, who was accused of helping moderate the forum, had his plea deferred by prosecutor Hugh Davies QC, as his counsel was not present.
Webber and Thomas were arrested in October 2009, after allegedly trying to pay a bill of around £1,000 in a central London hotel, using stolen credit card details. They failed to turn up at Belgravia police station in December, in breach of bail, having flown to Palma in Majorca. They were arrested in January at Gatwick, having flown back into the country on their passports.
In their possession they had a laptop, which allegedly contained over 100,000 credit card details. This could have lead to total losses of up to £12m to credit card companies, according to prosecutors. Police are still examining evidence.
On Friday Gary Kelly pleaded guilty to assembling and running a network of compromised computers, or botnet, linked to the Ghostmarket.net forum. Kelly also distributed a variant of the Zeus information-stealing Trojan.
Shakira Riccardo and Samantha Worley pleaded guilty to handling proceeds from the forum through two Halifax building society accounts. Worley had an account in the name 'J Worley', while Riccardo had an account under the name of 'C Birmingham'.
All of the defendants were under 23 years old.
Judge John Price told the court that the male defendants were all young and well educated.
"You're all very young people," Judge Price said. "It's a tragedy to see you in the dock. You've used your enormous skills and education in what looks like an enormous conspiracy to defraud — and you're all so young."
Judge Price said he would "give full credit" for the defendants' decisions to plead guilty, but warned there may be custodial sentences.
"These matters are so serious, there may be imprisonment," Judge Price said.
Webber, Kelly, and Thomas were remanded in custody, and Thomas will enter his plea on 29 November. Webber and Kelly will be sentenced on 28 February, with Riccardo. Worley will be sentenced on 14 December.