Hackers targeted Monobank, Ukraine's largest mobile-only bank, with waves of denial of service (DDoS) attacks on Jan. 21, the company's co-founder and CEO Oleh Horokhovskyi reported.
DDoS attacks direct excessive amounts of traffic at a website in order to overload its servers, often causing disruptions to service.
Horokhovskyi said Monobank was targeted with 580 million service requests in one attack.
"I think today Monobank is one of the most attacked IT targets in the country," he said.
Horokhovskyi had also reported a DDoS attack of 50 million service requests the previous day, Jan. 20.
While Horokhovskyi said the situation was under control and Monobank was "still standing," he said that another wave of attacks began as he was writing his announcement.
Horokhovskyi did not say who he thought was behind the attacks, though previous threats have been linked to Russian hackers.
Monobank was hacked on Dec. 12, the same day that a massive cyberattack targeted Ukrainian phone operator Kyivstar. The Russian hacker group Solntsepek claimed credit for the attacks against Kyivstar.
Russia has launched thousands of cyberattacks against Ukrainian organizations since the start of its full-scale invasion.