In a document, Assistant U.S. Attorney Stephanie S. Christensen said other hackers were aware of Mr. Monsegur's true identity, even though he often used a nickname or online personality while communicating with them.

WSJ: FBI's 'Sabu' Hacker Was a Model Informant

Calling themselves the "Dragonfly Army, " after Mr. Sukrit's nickname, Chinese fans have also teamed up with their Thai counterparts to form powerful online voting blocs that sway the outcome of Thai entertainment awards.

WSJ: Hungry for Drama, Chinese Viewers Send Out for Thai