Microsoft on Friday revealed that it was the target of a nation-state attack on its corporate systems that resulted in the theft of emails and attachments from senior executives and other individuals in the company's cybersecurity and legal departments.

The Windows maker attributed the attack to a Russian advanced persistent threat (APT) group it tracks as Midnight Blizzard (formerly Nobelium), which is also known as APT29, BlueBravo, Cloaked Ursa, Cozy Bear, and The Dukes.

Ransomware groups are constantly devising new methods for infecting victims and convincing them to pay up, but a couple of strategies tested recently seem especially devious. The first centers on targeting healthcare organizations that offer consultations over the Internet and sending them booby-trapped medical records for the “patient.” The other involves carefully editing email inboxes of public company executives to make it appear that some were involved in insider trading.