A WhatsApp group chat was used to send hundreds of millions of euros in cash around the world, funding organised crime and extremism with no paper trail, an investigation by European broadcasters has found.
The 532-member group chat, called "Traders of Greater Europe", was used to arrange cash transfers across borders for their clients, including to British cities such as Birmingham and London.
In one case, payments from Brussels went to militants from the Islamic State group (IS) in Syria.
The European Broadcasting Union (EBU) investigative journalism network, external, which includes the BBC, also found wider evidence of similar cash transfer systems being used in people smuggling and drug trafficking.
The group chat, which contained more than 82,000 messages sent between late February and December 2022, was first uncovered by Belgian investigating magistrate Vincent Guerra. An investigating magistrate is a judge who examines evidence in complex cases before trial and makes a recommendation about whether they should proceed.
Guerra said the number of transactions was "staggering" and the network covered "the entire planet". The case began as an investigation into terror financing, but "it became just a drop in the ocean of transactions", he said.
Members of the group chat sent messages in Arabic to each other to set up cash payments using the ancient hawala transfer system. Hawala involves a network of trusted money brokers who can arrange for funds to be sent around the world without any electronic record or physical transport of bank notes.
The system involves an agreement between two brokers, known as hawaladars, in different locations. One of the hawaladars is paid a sum of cash and the other agrees to supply the same sum, minus commission, to the recipient. The hawaladars agree to settle up all their transactions between themselves at a later date.
Hawala transfers are frequently used for legitimate purposes, such as immigrant workers sending funds home to support their families in countries with limited access to banks.
But criminals can also take advantage of hawala transfers to avoid the Swift system used for most international money transfers, where banks typically flag large transactions outside the normal course of business and are required to report any suspicious activity.
The Great Traders of Europe group was reserved for transactions over €5,000 (£4,279) and payments were often much larger. There is no indication that all those participating in the group were involved in handling criminal funds.
Hawala is illegal in many countries, including most of the EU, but is legal in the UK as long as the brokers are registered with Revenue and Customs (HMRC).
The cache of WhatsApp messages was obtained by the EBU following a 2024 court case in Belgium which convicted six money launderers, including Abu Adam, the head of the network in Brussels, and his number two, Abu Ahmed.
Belgian police had discovered evidence that the defendants had been sending money to IS, which was intended to help the wives of militants escape from detention camps in Syria. When they arrested Abu Adam, they discovered the Traders of Greater Europe group chat on his phone.
Guerra said it was like "hitting the jackpot", uncovering the inner workings of a vast, underground system. The phone also contained 6,000 photos of €5 notes showing the serial numbers and 6,000 photos of identity cards. These details are often used as unique identifying codes in hawala transactions, and the total number of notes and ID cards suggest Abu Adam had processed at least 12,000 transactions, Guerra said.
"This isn't just amateur work; it's professional, and at a level we could never have imagined," he said. "They're bankers with no government oversight."
The EBU also found further gangs across Europe using the hawala system for criminal activity. One former money launderer previously involved in European hawala networks, whom we are calling Frank, told the EBU he had been involved in transactions totalling several hundred million euros.
His first introduction to the hawala system had been at an office in a small town outside Rotterdam, he said. There, five or six messengers had arrived with money in about an hour and a half, transferring at least a million euros, he estimated.
"What I found out later is that it's not just about money. It's about the financing of terror. It's about drug trafficking. It's about prostitution and all sorts of other crap, to put it nicely," he said.
Cases in Austria have also revealed how the hawala system is bound up with people smuggling and violence.
In one case investigated by Austrian broadcaster ORF, part of the EBU network, Austrian police raided what they called "the biggest hawala office in Vienna". It was run from a kebab restaurant on a busy thoroughfare and which authorities say was used to make payments for people smuggling.
Two Syrian brothers who ran the operation were charged with human trafficking, as well as torturing and raping a courier who had lost €350,000 (£300,000), saying he had been robbed. They were convicted last year and sentenced to 18 and 8 years in prison respectively.
Austrian police and Europol also recently dismantled another people-smuggling ring financed through hawala, which officials said had transported about 100,000 people into Europe over 18 months.
Gerald Tatzgern, who leads human-trafficking investigations at Austria's Criminal Intelligence Service, the BK, told ORF that torture was a reality of people smuggling and was also used to maximise profits.
He said: "Videos of the torture are then sent to the families, saying that if they don't send another €1,000 or several thousand euros, then the person concerned - your son, your brother, your father - will suffer."
Payments to stop the torture were demanded through the hawala system, he said.
Police commander and Europol liaison officer Quentin Mugg, who has led a number of money-laundering investigations, said the hawala system was "the primary money-laundering channel for organised crime".
"Whether the money comes from migrant smuggling, human trafficking, pimping, a grandmother's savings sent as a birthday present to her son, or a Malian working in France who wants to support his family, [the hawaladars] couldn't care less," he said. "And they'll apply their rates."
