MOSCOW (AP) — Russia's biggest cybersecurity firm says that its manager in charge of investigating hacking attacks has been arrested.

An employee works near screens in the virus lab at the headquarters of Russian cyber security company Kaspersky Labs in Moscow Thomson Reuters A key cybercrime investigator at Russia's biggest cybersecurity firm, Kaspersky, was arrested on charges of treason last month, Russia's Kommersant newspaper reported on Wednesday.

Kaspersky Lab confirmed to the Associated Press that Ruslan Stoyanov, head of its computer incidents investigations unit, was arrested in December.

Stoyanov was arrested along with a senior Russian FSB intelligence officer, Sergei Mikhailov, according to Kommersant. Mikhailov, who also faces treason charges, was the deputy head of the information security department of the FSB, Russia's national security service.

Investigators are examining money that Stoyanov allegedly received from foreign companies or entities, according to Kommersant. A source told the paper that the case has been filed under article 275 of Russia's criminal code, which allows the government to prosecute an individual suspected of aiding a foreign state or organization.

"Stoyanov was involved in every big arrest of cybercriminals in Russia in past years," a source familiar with Stoyanov's past work told Forbes.

Kaspersky said in a statement posted on its website that "the case against this employee does not involve Kaspersky Lab."

"The employee, who is Head of the Computer Incidents Investigation Team, is under investigation for a period predating his employment at Kaspersky Lab," the statement continued. "We do not possess details of the investigation. The work of Kaspersky Lab’s Computer Incidents Investigation Team is unaffected by these developments.”

Kaspersky Lab is a leading cybersecurity firm that helps millions of people worldwide, including Americans, protect their data from cybercriminals. While the firm is often aggressive in its pursuit of foreign hackers, however, it doesn't pursue alleged Russian cyber operations "with the same vigor," according to a 2015 Bloomberg investigation.

Eugene Kaspersky, the firm's billionaire founder and CEO, was educated at a KGB-sponsored cryptography institute before working for Russian military intelligence. He reportedly maintains relationships with former and current Russian intelligence officials, but has pushed back against claims that his company works with the Kremlin.

'Treason charges are by no means rare'

Stoyanov's previous jobs, listed on LinkedIn, include a position at the Moscow Cyber Crime Unit at the Russian Interior Ministry that he held between 2000-2006. He moved into the private sector to work at Kaspersky in July 2012, according to his LinkedIn page.

It wasn't immediately clear if the arrests are somehow linked to the US intelligence community's conclusion that Russian hackers, at the Kremlin's order, broke into Democratic National Committee servers and Hillary Clinton campaign chairman John Podesta's inbox during the election.

"Treason charges are by no means rare (see this case or this even more farcical one, which in fairness was eventually tossed out), so it is hard to know at this stage what is involved," Mark Galeotti, a senior research fellow specializing in Russian security affairs at the Institute of International Relations Prague, said in an email.

"But simply the suspicion of passing information to foreigners for cash or carelessly might be enough," he added.

Andrei Soldatov, however, who has studied the internet and Russian security services for more than a decade, called the arrest of the Kaspersky manager "unprecedented."