Stanislav Lisov, a computer programmer, was wanted by US authorities, a spokesman for the Guardia Civil police force said.
"He is accused of conspiracy to commit fraud via electronic media and conspiracy to commit fraud and abuse with computers," a spokesman for Spain's top-level National Court added.
Lisov was detained last week in Barcelona's El Prat airport when he was about to board a flight, police said.
He was jailed on January 13th after being questioned via videoconference by a judge in Madrid's National Court, which investigates suspected crimes that have an international remit.
The judge decided to put him in prison as he does not live in Spain and could escape, and due to the "gravity of the offences."
"Now begins the process of extradition to the United States," the National Court spokesman said, without giving further details.