Personal information of hundreds of customers at cryptocurrency exchange Bithumb has been leaked in a recent cyberattack, industry sources said Thursday. Bithumb reported a data breach in its in-house mobile system on Wednesday, but the incident was initially believed to have affected only its employees. After analyzing the scope of the data leak, Bithumb found that personal information of hundreds of customers has also been exposed, according to the sources. Three financial firms — Daishin Securities, Mirae Asset Global Investments and Bithumb — have been hit by cyberattacks, in the latest hacking attack targeting the nation's financial institutions.