New York (CNN Business) Microsoft is suing a mysterious North Korean hacking group for allegedly stealing "highly sensitive information" from computers in the United States.

Microsoft MSFT A new lawsuit targets two unnamed people whoclaims work for Thallium, which the suit describes as a "cybertheft operation" that has worked to gain access to "high-value" computer networks.

Thallium targeted government employees, think tanks, university staff and members of groups that work on issues including nuclear proliferation and human rights, the complaint states. Microsoft filed the lawsuit on December 18 and it was unsealed late last week.

It's not clear how many people Thallium may have hacked, though the complaint alleges the group "has been active since 2010, and it poses a threat today and into the future."

Microsoft is asking for companies that host website domains associated with Thallium to hand over control of the sites. It also wants compensation for damages in "an amount to be proven at trial." Microsoft did not immediately respond to a request for comment.

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