Liberty Reserve 'provided anonymous payments'
The American authorities have accused a financial service called Liberty Reserve of money laundering on a grand scale.
Prosecutors say that the service, often called a digital currency exchange, is turning criminal profits into untraceable funds on its digital exchange, meaning they can be used for financial transactions without any trace of their origin.
Liberty Reserve is based in Costa Rica, but the American Justice department believes it can stop its activities.
Dr Damon McCoy, of the computer engineering department at George Mason University in Virginia, told the Today programme's James Naughtie that "it appears that there was a lot of ill-gotten money being transferred though this service".
First broadcast on BBC Radio 4's Today programme on Wednesday 29 May 2013.