Microsoft Cloud Email Breach

As much as Microsoft has expanded to become a leading cybersecurity vendor by just about every measure, the company’s widely deployed applications and vast client base continue to be appealing targets for malicious actors. This week, the Redmond, Wash.-based tech giant revealed that attackers recently succeeded at compromising the defenses around its cloud email service, though the disclosure of the breach omitted a number of important specifics. Other organizations have filled in some of the gaps, including the U.S. Cybersecurity and Infrastructure Security Agency (CISA). The breach was discovered after a U.S. federal civilian agency “identified suspicious activity in their Microsoft 365 (M365) cloud environment,” and reported it to Microsoft, CISA said in a post.

[Related: The 10 Biggest Data Breaches of 2023 (So Far)]

Notably, Microsoft did offer attribution for the attack, pinning the breach on a hacking group working on behalf of the Chinese government. At least two U.S. government agencies are reportedly among the victims.

Microsoft said in its post that it has “completed mitigation of this attack for all customers,” and that customers do not have to take any action in response. “If you have not been contacted, our investigations indicate that you have not been impacted,” the company said.

What follows are five key things to know about the Microsoft cloud email breach.