A U.S. cybersecurity company says Russian military agents successfully hacked the Ukrainian gas company at the center of the scandal that led to President Donald Trump's impeachment. 

Russian agents with the Main Intelligence Directorate of the General Staff of the Russian Army, better known as the GRU, launched a phishing campaign in early November aimed at stealing the login credentials for employees of Burisma Holdings, the gas company. That's according to Area 1 Security, a Silicon Valley company that specializes in e-mail security.

It is not clear what the hackers were looking for or may have obtained, although the operation's timing suggests that Russian agents may have been searching for material that could damage former Vice President Joe Biden, whose son Hunter previously served on Burisma's board.

The Associated Press reports the GRU was the same military unit that hacked emails from the Democratic National Committee and the chairman of Hillary Clinton’s campaign during the 2016 presidential race.

The details of the alleged hacking against Burisma were outlined in this eight-page report.

RELATED: Ahead of impeachment trial, Trump suggests not having it

RELATED: As trial nears, Trump keeps discredited Ukraine theory alive

Trump was impeached in December for abusing the power of his office by urging Ukraine's president to investigate Biden, his potential opponent in the 2020 general election. Trump was impeached on a second article for obstructing the House's investigation. The Senate is expected to receive the articles this week in order to launch a trial.

Phishing involves a hacker sending an email to lure the victim to a fake website that looks like a familiar one. Then the hacker tricks the victim into providing login information as well as personal information.

Area 1's clients include candidates for U.S. federal elected offices, according to AP. It's CEO said top candidates in the presidential and congressional races have been targeted by about 1,000 phishing emails in recent months.