Cybercrime police in the Netherlands have arrested four men for allegedly stealing $1.4 million from banking customers and then using Bitcoin in an attempt to launder the funds.

According to Information Week, the men are accused of employing the banking malware known as TorRAT, a remote-access Trojan designed to steal online banking information and which receives command-and-control instructions via the anonymizing Tor network. Tor lets the botnet's operators disguise the commands they send to infected PCs and hide the flow of stolen data being transmitted from infected PCs to attacker-controlled servers, the site said.

Stealing the funds was easy, but converting to cash was much more difficult. "It is relatively straightforward to manipulate bank transactions on an infected computer," Trend Micro senior threat research Feike Hacquebord wrote in a blog post. "But you need mules for laundering stolen money."

The Dutch gang allegedly laundered money through Bitcoin transactions and even set up their own Bitcoin exchange service, Information Week said.

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