In a recent regulatory filing, Microsoft Corp. (NASDAQ:MSFT) revealed that the email accounts of its top executives were breached by a Russian intelligence group. What Happened: Microsoft’s regulatory filing states that Nobelium, the Russian intelligence group responsible for the 2020 SolarWinds breach, accessed the email accounts of several top Microsoft executives. Microsoft discovered the breach last week, as it noted on its security blog on Friday. “The attack was not the result of a vulnerability in Microsoft products or services. To date, there is no evidence that the threat actor had an…