The commission said that when users logged into other company's services using their Facebook accounts, the personal information of their Facebook friends was also shared to such service providers without consent.
The personal information that was shared with other companies included users' names, their addresses, dates of birth, work experience, hometowns and relationship statuses.
The watchdog said the exact amount of the shared information is unclear as Facebook did not provide relevant documentation.
Considering the information could be provided to at most 10,000 other companies, the watchdog said a considerable amount of personal information could have been shared.
The commission said it will refer Facebook Ireland Ltd -- which was in charge of Facebook operations in South Korea from May 2012 to June 2018 -- to the prosecution for a criminal investigation.
Facebook Ireland's director in charge of user privacy could face up to five years in prison or a maximum of 50 million won in fines if convicted of violating South Korea's relevant personal information law.
It added that Facebook was uncooperative in its investigation as it submitted incomplete or false documents.
The commission also levied Facebook with a separate penalty of 66 million won for the false documentation.
Facebook expressed regret at the commission's move.
"We cooperated with the investigation in its entirety," Facebook said in a statement. "We have yet to closely review PIPC's measure."
In 2018, the Korea Communications Commission, South Korea's telecommunications regulator, started investigations into Facebook before handing it off to the commission.
(Only the headline and picture of this report may have been reworked by the Business Standard staff; the rest of the content is auto-generated from a syndicated feed.)
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