Russian software developer Microolap confirmed that hackers had compromised some of its systems but denied claims that they gained access to its network monitoring platform or stole data belonging to major Russian companies.

Microolap, which develops software for intercepting and analyzing network traffic, said Thursday that it had detected an attempted breach of several non-critical systems but found no evidence that hackers accessed its core infrastructure, customer data or other sensitive information.

"We urge people not to treat the attackers' claims as fact," Microolap CEO Andrey Smirnov said. "Our cybersecurity systems worked as intended: We detected the incident and kept critical data secure."

The statement came a day after a hacking group calling itself Black Spark claimed it had spent more than a month inside Microolap’s network and gained access to its internal systems, including EtherSensor, the company's network traffic analysis platform.

The hackers claimed they extracted and deleted data belonging to several Microolap customers, including Russian Railways, state banknote and document producer Goznak, VTB Bank and its leasing subsidiary, and Russian IT company NEK.TECH.