Assistant Attorney General Leslie R. Caldwell for the Justice Department's Criminal Division and U.S. Attorney Preet Bharara of the Southern District of New York made the announcement.

Mark Marmilev, 35, of Brooklyn, New York, pleaded guilty today before U.S. District Judge Denise L. Cote to conspiring to operate an illegal unlicensed money transmitting business that he knew involved the transmission of funds derived from criminal activity. Sentencing is scheduled for Dec. 12, 2014.

"Marmilev designed and maintained a massive criminal infrastructure in cyberspace for one of the world's most widely used digital currency systems, which laundered billions in criminal proceeds," said Assistant Attorney General Caldwell. "This is the third conviction in the largest international money laundering case ever brought by the department, and we will continue to ensure that virtual currencies are not misused to facilitate criminals hiding from the U.S. justice system."

"As the chief technology officer of Liberty Reserve, Mark Marmilev was responsible for the infrastructure of a global payment processor and money transfer system that catered largely to criminals," said U.S. Attorney Bharara. "With his guilty plea today, we are one step closer to holding to account everyone integrally involved in this sprawling Internet enterprise that served as a central financial institution for cyber criminals and illegal transactions of numerous kinds."

According to allegations contained in the indictment and statements made in related court proceedings, Liberty Reserve was incorporated in Costa Rica in 2006 and billed itself as the Internet's "largest payment processor and money transfer system." Liberty Reserve was created, structured and operated to help users conduct illegal transactions anonymously and launder the proceeds of their crimes, and it emerged as one of the principal money transfer agents used by cybercriminals around the world to distribute, store, and launde, and launder the proceeds of their illegal activity. Liberty Reserve was used extensively for illegal purposes, functioning as the bank of choice for the criminal underworld because it provided an infrastructure that enabled cybercriminals around the world to conduct anonymous and untraceable financial transactions.

According to court records, before being shut down by the government in May 2013, Liberty Reserve had more than one million users worldwide, including more than 200,000 users in the United States, who conducted approximately 55 million transactions through its system totaling more than $6 billion in funds. These funds encompassed suspected proceeds of credit card fraud, identity theft, investment fraud, computer hacking, child pornography, narcotics trafficking and other crimes. Marmilev was an associate of Liberty Reserve founder Arthur Budovsky and served as Liberty Reserve's chief technology officer. In that role, Marmilev was principally responsible for designing and maintaining Liberty Reserve's technological infrastructure.

Marmilev and Budovsky were among seven individuals charged in the indictment, which was unsealed on May 28, 2013, and two co-defendants - Vladimir Kats and Azzeddine el Amine - previously pleaded guilty and await sentencing. The indictment also charged Liberty Reserve with conspiracy to commit money laundering and operation of an unlicensed money transmitting business, and the charges remain pending.

This case is being investigated by the U.S. Secret Service, the Internal Revenue Service-Criminal Investigation, and the U.S. Immigration and Customs Enforcement's Homeland Security Investigations, with assistance from the Secret Service's New York Electronic Crimes Task Force. The Judicial Investigation Organization in Costa Rica, the National High Tech Crime Unit in the Netherlands, the Financial and Economic Crime Unit of the Spanish National Police, the Cyber Crime Unit at the Swedish National Bureau of Investigation and the Swiss Federal Prosecutor's Office also provided assistance.

This case is being prosecuted jointly by the Criminal Division's Asset Forfeiture and Money Laundering Section (AFMLS) and the U.S. Attorney's Office's Complex Frauds Unit and Asset Forfeiture Unit in the Southern District of New York, with assistance from the Criminal Division's Office of International Affairs and Computer Crime and Intellectual Property Section.

Trial Attorney Kevin Mosley of AFMLS and Assistant U.S. Attorneys Serrin Turner, Andrew Goldstein and Christine Magdo of the Southern District of New York are in charge of the prosecution, and Assistant U.S. Attorney Christine Magdo is in charge of the forfeiture aspects of the case.

The charges contained in the indictment against certain of Marvilev's co-defendants remain pending and are merely accusations. Those defendants are presumed innocent unless and until proven guilty.