(Reuters) - The February hack at UnitedHealth's Change Healthcare unit affected the data of 100 million people, the U.S. health department's website showed, making it the largest data breach in the country.

UnitedHealth did not immediately respond to a Reuters request for comment.

The Change Healthcare unit was breached by a hacking group called ALPHV, also known as "BlackCat." UnitedHealth first reported the breach on Feb. 21.

In June, UnitedHealth issued a public notice about the ransomware hack as part of its requirements to notify the estimated one-third of the country whose private data may have been exposed in the attack.

(Reporting by Manas Mishra in Bengaluru; Editing by Alan Barona)