The ESB said that security of the electricity supply was a key priority

Hackers believed to be linked to the Russian government have attacked Ireland’s energy sector.

Senior ESB engineers were targeted last month by a group understood to have ties to the Kremlin’s GRU intelligence agency with a highly specific email, seen by The Times, that contained malicious software.

There is no evidence of disruption to the network but security analysts monitoring Russia’s cyberintelligence groups said that the hackers were likely to have stolen internal information including engineers’ passwords.

Experts said that Ireland was being used as a testing ground for cyberwarfare by GRU teams and potentially as one of several EU countries that Russia may look to destabilise.

US officials confirmed last week that Russian government hacking teams had penetrated American nuclear and other energy