Peter Levashov, 37, was due to appear before a federal judge in Connecticut where he faces hacking, wire and email fraud, identity theft and conspiracy charges.
Prosecutors say Levashov ran the “Kelihos” botnet, a network of thousands of infected computers used to harvest internet login credentials, distribute bulk spam emails sometimes used for fraudulent “pump-and-dump” stock promotions and install malicious software on unsuspecting users' computers.
In any given 24-hour period, Levashov's network allegedly generated more than 2,500 spam emails advertising such schemes as services to other potential cyber-criminals.
John Cronin, the acting head of the Justice Department's criminal division, said in a statement that the extradition proved the US would hunt down international cyber-criminals and “hold them accountable for their conduct.”
Originally from Saint Petersburg, Levashov was arrested at Barcelona airport on April 7 by Spanish authorities acting on a US warrant. Spain's High Court authorized his extradition in October.
Levashov's lawyers in Spain said he had served in the Russian army and worked for President Vladimir Putin's United Russia party.
They argued he feared being forced to turn over confidential information to American authorities, but Spanish judges rejected these claims.