Ukrainian hackers claim to have destroyed a data center used by thousands of Russian businesses and its military.

A hacking group known as Blackjack says it worked with the cyber department of the Security Service of Ukraine (SBU) to take down the OwenCloud.ru data center.

The location of the data center has not been disclosed but the hackers say they destroyed 300TB of data held on 400 virtual and 42 physical servers.

Details of the attack were first reported by the Kyiv Independent, which cited an SBU source. However, the publication said it has been unable to verify the claims.

OwenCloud.ru’s homepage reportedly displayed a message stating it had been hacked following the attack on Monday, April 8. It said the provider’s "IT infrastructure has been destroyed," adding: “You work in the interests of the Russian Defense Ministry – you are a legitimate target.”

However, the service now appears to be operating normally.

Organizations impacted by the hack span businesses in the oil and gas and telecoms sectors, as well as the country's military. Victims listed in the Kyiv Independent report include Ural Works of Civil Aviation, Rubin, Ural Plant Spectechniks, Gazprom, Transgaz, Lukoil, Rosneft, Nornickel, Rostelecom, and MegaFon.

The report says the attack was in retribution for strikes by Russia on Ukraine’s digital infrastructure which have taken place throughout the war between the two countries, including a reported cyberattack against the Parkovyi data center in January.

In December, Ukraine’s biggest mobile operator Kyivstar was hit by an attack that left millions of customers without network coverage. This breach was blamed on Russian hackers.

Last year DCD reported that Russia had inflicted $1.79 billion worth of damage on Ukraine’s telecoms infrastructure during the war.