In cyberwarfare, the toughest question to answer definitively is: “Who did it?” It’s no surprise then that Microsoft avoided the attribution on everyone’s lips in its analysis of last week’s cyberattacks on Ukraine. That would be Russia. But several clues suggest they not only came from the Kremlin but will follow a pattern of spilling into other countries in Europe, the US and across the world. That ratchets up geopolitical tension: Ukraine is now bracing for potential military action from Moscow; Russian President Vladimir Putin has 100,000 troops at the border; and Moscow’s security talks with the US and Nato have broken down.

There’s a lot of circumstantial evidence for a Russian hand in the latest cyberattacks, which affected around 70 government agencies in Ukraine, the worst in the country in four years. They resemble a devastating series that was widely attributed to Moscow, which began in 2015, continued into 2017 and swamped Ukraine’s banks, media and electric utilities with malware targeting Windows-based systems. If so, the wider world outside Ukraine had better start taking precautions...