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Rio de Janeiro • Doyen Sports Investments, one of the biggest firms in the now-banned soccer player futures market, says scores of sensitive documents were leaked online by hackers because it didn't give in to their unspecified demands.

The documents published on Football— provide an unprecedented glimpse into a largely secretive practice in which investors loan money to often cash-strapped soccer teams in return for a percentage of the fees they get when a player is traded to another team.

FIFA, the governing body for world soccer, banned investors last year from the $4 billion global player trading market amid complaints funds were exerting too much influence.

Doyen Sports has grown in recent years to become a major investor in top soccer talent from Brazil to countries across Europe.

Its other interests include player management, consulting and investing in image rights of players, including Barcelona and Brazil forward Neymar, one of soccer's biggest talents.

The documents, including banking details, outline how much the firm paid for each of its agreements; $6.35 million in the case of Neymar.

"Doyen Sports and its business partners have been subject to numerous attacks on their privacy by the "Football Leaks" website," according to an e-mailed statement Wednesday from the firm.

The company said that some of the documents, obtained in a cyber attack on its servers, were authentic while others were manipulated "to increase the media and the public's interest."

The firm had received demands from the authors of the Football Leaks website, whose identities aren't publicly known, and has been subject to an increasing number of leaks because it "did not give in to the pressure and demands," according to the statement.

"Doyen Sports has taken the appropriate measures to identify those responsible for this attack, whilst we reiterate our position: We have nothing to hide, we act purely according to principle and in defense of the institutions and people we work with, namely the football clubs who are our main partners," according to the statement.

The company said it has handed the case over to authorities. Most of the leaks published relate to soccer clubs in Portugal. The Portuguese national police force didn't respond to an e-mail seeking comment.

Among the leaks were Doyen's accounts for the second half of 2011.

They revealed the company has been involved in some of soccer's richest trades and turned a handsome profit. The company invested $27.4 million for trading rights for seven players, including some of the sport's most expensive.

Doyen spent $10.7 million for a 33.3 percent stake in Colombian striker Radamel Falcao's trading rights. When he was traded two years later, the company netted a $4.3 million profit. The firm also loaned $7.5 million to two Spanish teams, Atletico Madrid and Sporting de Gijon.

The FIFA ban on investors buying stakes in future trading rights is the biggest part of Doyen's business.

The practice — called third-party ownership — started in South America and has spread to large parts of Europe, raising concerns about investors' influence over the sport. Doyen has challenged the ban in court.

The leaked documents also reveal the source of the company's funding to be two entities that share an address with Doyen Sports in Ta'Xbiex, a town in Malta.

One of the companies, Benington Group Assets Limited, has a single shareholder, Malik Ali, a Turkish citizen in his early 30s.

Ali, who loaned more than $58 million to Doyen, according to one of the documents, also owns all of Doyen's Class A shares. The remaining 20 percent of its stock is in Class B shares, owned by another Maltese entity called Wood, Gibbins & Partners Limited.

The latest batch of documents show a Kazakh named Refik Arif made a seven-year loan of 100 million euros to Ali at an interest rate of 4.5 percent, the same as Ali charges Doyen.

The leak comes at a sensitive time for Doyen.

As well as the case against FIFA, it's awaiting the result of a lawsuit at the Court of Arbitration for Sport after Portugal's Sporting Clube refused to pay the fund profits it was due over the trade of Argentine defender Marcos Rojo to Manchester United. Sporting claims the contract with Doyen is abusive.

While the exact size of Doyen is unknown, Chief Executive Nelio Lucas said in 2014 that the company turns over considerable amounts of cash, though it remains small compared with the parent company.

"The group is backed from private families," he said. "It's very clear we have so many investments in so many things. So many billions in turnover. So 100 million it's a little drop in the ocean. Now 200 million, that's two drops in the ocean."