Hackers brought down the power supply to hundreds of homes in Ukraine last week, in a cyber attack believed to be the first ever to result in a power outage. The Ukrainian energy ministry said it was probing a “suspected” cyber attack on the power grid, targeting several regional power companies, which the country’s intelligence service blamed on “Russian special services”. Moscow has not responded to the allegation. John Hultquist, head of cyber espionage intelligence at iSight partners, a US-based threat intelligence company, said it was the first time the cyber security industry had seen a cyber attack result in the shutdown of power. Experts have warned for years that the industrial systems that control critical infrastructure such as power plants are vulnerable. Malicious software, known as malware, has previously been discovered on these networks, but no one has yet linked these infections to an outage. Mr Hultquist said that the versions of the malware used in the attack, called BlackEnergy, point to Russian hackers known as the Sandworm team who have previously infected power suppliers in the US and Europe. The malware was found in the west in 2014 and is thought to have been wiped from the targets’ networks.