TALLINN — On the eve of another European winter, one of Russia’s most skilled, stealthy hacking groups is targeting the Continent’s energy infrastructure. Sandworm, a group linked to Russian intelligence, has been hacking Ukrainian targets in recent years, but “we’re now seeing that they’re interested in the energy sector across Europe,” Jamie Collier, lead threat intelligence adviser at Google, told POLITICO. “With the onset of winter, that’s clearly a concern,” Collier added. The Sandworm group is one of the Kremlin’s most notorious cyberthreats, often working in the shadows. Western intelligence previously tied the group to a 2015 attack that took…