Healthcare data and personal information of more than 100 million people was stolen in the ransomware attack on Change Healthcare in February, UnitedHealth has confirmed for the first time.

The February hack at UnitedHealth's tech unit Change affected the personal information of 100 million people, the U.S. health department's website showed, making it the largest healthcare data breach in the country.

UnitedHealth, the largest U.S. health insurance provider, blamed a Russia-based ransomware gang for the huge data breach of U.S. medical data.