Microsoft informs customers that Russian hackers spied on emails

The disclosure underscores the breadth of the breach as Microsoft faces increasing regulatory scrutiny over the security of its software and systems against foreign threats. An allegedly Chinese hacking group that separately breached Microsoft last year stole thousands of US government emails.

The Russian government has never responded to the Microsoft hacking allegations, but Microsoft has said the hackers targeted cybersecurity researchers who had been investigating the Russian hacking group's actions.