Microsoft programs including its mail and calendar services were recently hacked by a group the company has “high confidence” is working for the Chinese Communist Party.

The hack prompted the U.S. Cybersecurity and Infrastructure Security Agency to issue a rare emergency directive that requires all government networks to undergo a software update.

The perpetrator, Microsoft outlined in a blog post, is a hacker group that the company has “high confidence” is working for the Chinese Communist Party and focuses on spying on American targets.

In another blog post, Microsoft Vice President Tom Burt noted that the hacking group has recently spied on a wide array of American targets, including “infectious disease researchers, law firms, higher education institutions, defense contractors, policy think tanks and NGOs.”