A recent data breach at Columbia University has exposed the personal information of nearly 900,000 individuals, including current students and applicants.

The breach came to light following a technical outage in June that disrupted several university systems. Columbia University notified those potentially affected in a data breach alert.

Initially, the university denied reports of a hacker attack hours after the outage. However, an investigation later revealed that cyber attackers had infiltrated Columbia’s systems more than a month before the outage.

“Our investigation determined that, on or about May 16th, 2025, an unauthorized third-party gained access to Columbia’s network and subsequently took certain files from our system,” the breach notification said.

Columbia informed the Maine Attorney General’s Office that the breach exposed data of more than 868,000 people. Since the university has about 34,000 students and over 7,000 faculty members, the high number suggests that alumni are likely among those affected.

The university emphasized that although attackers did infiltrate Columbia’s systems, there is no evidence that patient records from the Columbia University Irving Medical Center were compromised.

However, the breach likely exposed data related to applicants and current students.