Recruited by cyber-criminals through seemingly legitimate job adverts, money mules use their bank accounts to transfer funds they have been sent by their ‘employers' to another account, often in another country.

This adds further complexity to law enforcement investigations, making the proceeds of crime harder to follow.

While most money mules are willing participants, some are oblivious to the fact that they are helping to fund criminality. And money muling helps perpetuate other crimes beyond money laundering – the stolen money may be funding other forms of organised crime such as drug dealing and human trafficking.

Over 90 percent of money mule transactions are linked to cyber-crime and, due to this critical role money mules play, are a current focus for Europol's European Cybercrime Centre (EC3), our law enforcement partners and the Joint Cybercrime Action Taskforce (J-CAT).

An example of this was on 14 November 2016, when EC3 worked with law enforcement agencies from 16 European countries, as well as the FBI, the US Secret Service, Eurojust and the European Banking Federation (EBF), to coordinate a week-long operation against criminals and criminal organisations that use this form of money laundering.

With 10 operational centres set up across Europe, law enforcement were able to cooperate closely with private sector partners, and vital information was provided by 106 banks and financial services companies on suspicious transactions they had detected. Financial investigators then worked to collect further sufficient evidence to identify the money mules. Once we had that, law enforcement agencies were able to make arrests on their territories.

In total, we identified 580 money mules, interviewed 380 suspects and arrested 178. From a law enforcement perspective, close cooperation with the banks and financial services companies was critical for increasing the impact of the investigations and disrupting the criminal groups.

This was the second global European Money Mule Action (EMMA) we carried out this year. The first took place in February and saw 81 arrested and over 700 money mules identified. The difference in results from the two operations suggests that the first reduced the average number of money mules operating at any given time, and that Europol and its partners became more effective at targeting individuals and gathering the evidence that led to the arrests.

An essential counterpart to investigation is prevention. This should not only entail preventing people from becoming new victims, but also dissuading would-be cyber-criminals from following that pathway.

We therefore had a coordinated prevention and awareness campaign – in nine European languages – to inform the public and other organisations about the scale of money muling and the legal consequences for the mules. Operational and strategic partners also joined Europol in raising awareness, running their own campaigns.

By making it harder for cyber-criminals to recruit money mules, Europol hopes to make cyber-crime less attractive to criminals.

* Steven Wilson is head of the European Cybercrime Centre (EC3) at Europol.