Authorities reportedly suspect the Russian national of handing state secrets about the country's Navy to the West.
The Russian president has also boasted about thwarting foreign intelligence activities in the past.
U.S. intelligence officials fear a mole exposed CIA spying operations in China, but American embassy employees have been targeted for years.
The U.S. embassy has said they are worried about the citizen's welfare.
The intelligence agency will send cryptography and cybersecurity puzzles to schoolgirls.
Shahram Amiri disappeared in 2009, surfaced in the U.S. but returned home to Iran in 2010.
For more than three years, the FBI pursued Keith Gartenlaub as a Chinese spy. So why is he now accused of collecting child pornography?
Unidentified officer in sensitive intelligence unit could possibly face the death penalty.
Aristidas Tamosaitis was detained in Moscow in May 2015.
Cuba has kept our missing missile and sent a spy to our security conference.
As a new book about the novelist John le Carré proves, writing the truth about a brilliant liar can get complicated.
The CIA provides the technology for a plane-assisted fake cell tower surveillance program.
Together, the NSA and GCHQ harvested encryption keys to access global mobile communications.
With little congressional involvement, the Justice Department is changing the rules about how law enforcement obtains warrants.
Former CAPO agent Uno Puusepp has been unveiled as a double agent for Russia's FSB
As reader-supported news vanishes, corporate-journalist hybrids may start drawing more red lines.