Russian authorities have reportedly charged two officers in the Federal Security Service and an employee of cyber security firm Kaspersky Lab with committing treason in the interests of the United States.
Ivan Pavlov identified the three as Ruslan Stoyanov, head of Kaspersky's computer incidents investigation team, and two officers working for the FSB's Information Security Centre, Sergei Mikhailov and Dmitry Dokuchayev.
"My client, along with the others, has been charged with state treason and cooperating with US intelligence services," Mr Pavlov, who represents a fourth suspect, said.
Mikhailov, head of cyber security at the FSB, was reportedly detained in a meeting in December, with officers grabbing him and putting a bag over his head before taking him away.
"In early December, FSB Colonel Sergei Mikhailov, who was responsible for cyberwars and cyberattacks… was arrested by the FSB; yes, with a bag over his head,” Sergei Markov, a member of the Public Chamber in the Russian parliament and adviser to the Kremlin, told The Daily Beast.
The arrests were made at a time of heightened tensions between Washington and Moscow after US intelligence officials accused Russian hackers of sabotaging last year's US election in favour of President Donald Trump.
Moscow denies the allegations.
Russian newspaper Kommersant first reported the arrests last week, which it said took place in December.
The Kaspersky team headed by Stoyanov has been cooperating with the FSB since 2013 in analysing cybercrime cases and offering expertise in criminal cases concerning cybersecurity, Kommersant reported.
Kaspersky Lab confirmed Stoyanov's arrest but said the charges related to a period before he joined the company in 2012.
A Kremlin spokesman said Russian President Vladimir Putin was aware of media reports about the arrests but the Kremlin could not confirm anything about them.
Vladimir Anikeev, a journalist said to have lived in Ukraine, have also been arrested, the Financial Times reported.
A Moscow court has said Mr Anikeev is being held in pre-trial detention until March 8, the newspaper said. Mr Anikeev, who denies all wrongdoing, faces charges of hacking unnamed victims’ private information.