When Brazilian K-pop fan Tami spotted a social media post last month selling a rare Polaroid photo signed by ZeroBaseOne member Zhang Hao, she jumped at the opportunity. The seller identified himself as a South Korean named Park Chae-ah, according to the Chosun Daily newspaper. She transferred the money. Then Park switched his account to private and vanished. Tamil is far from alone. Across Brazil, home to one of Latin America’s most passionate Korean pop culture communities, scammers have found...