SEOUL, South Korea — South Korea’s privacy watchdog on Tuesday fined social media company Meta $15 million for illegally collecting sensitive personal information from Facebook users, including data about their political views and sexual orientation, and sharing it with thousands of advertisers.

Following a four-year investigation, South Korea’s Personal Information Protection Commission concluded that Meta unlawfully collected sensitive information about around 980,000 Facebook users, including their religion, political views and whether they were in same-sex unions, from July 2018 to March 2022.

It said the company shared the data with around 4,000 advertisers.

South Korea’s privacy law provides strict protection for information related to personal beliefs, political views and sexual behavior, and bars companies from processing or using such data without the specific consent of the person involved.

The commission said Meta amassed sensitive information by analyzing the pages the Facebook users liked or the advertisements they clicked on.

The company categorized ads to identify users interested in themes like specific religions, same-sex and transgender issues, and issues related to North Korean escapees, said Lee Eun Jung, a director at the commission who led the investigation on Meta.

“While Meta collected this sensitive information and used it for individualized services, they made only vague mentions of this use in their data policy and did not obtain specific consent,” Lee said.

Lee also said Meta put the privacy of Facebook users at risk by failing to implement basic security measures, such as removing or blocking inactive pages. As a result, hackers were able to use inactive pages to forge identities and request password resets for the accounts of other Facebook users. Meta approved these requests without proper verification, which resulted in data breaches affecting at least 10 South Korean Facebook users, Lee said.