Russian government hackers tried but failed to attack Poland's energy grid last December, TechCrunch reported on Thursday.

Poland's Energy Ministry said the hackers targeted two combined heat and power plants between Dec. 29 and 30 and sought to disrupt communications between wind turbines and power distribution operators. If the attack had succeeded, at least 500,000 households across Poland could have suffered power outages, TechCrunch reported, citing local media.

Cybersecurity firm ESET said its analysis of the destructive malware DynoWiper used in the attack suggests it was likely carried out by Sandworm, a hacking group linked to Russia's military intelligence agency, the GRU. Sandworm has previously attacked Ukraine's energy infrastructure and caused large-scale blackouts, and the latest attack proceeded in a similar way.

DynoWiper is wiper malware that permanently deletes computer data and cripples systems, and is characterised by directly targeting energy infrastructure.

The incident occurred around a similar time of year to Sandworm's 2015 attack on Ukraine's power grid that left 230,000 households without electricity. Several areas, including the Ukrainian capital Kyiv, were affected at the time, and the same type of attack recurred a year later. Polish Prime Minister Donald Tusk said, "Our cyber defence system worked effectively, so critical infrastructure was not threatened." Experts warned that Russian cyberattacks are becoming increasingly sophisticated and that threats targeting energy infrastructure are likely to persist.