Billionaire's value drops as trader calls his firm 'fraud'

US billionaire Robert Pera's net worth fell by $248 million on Monday to $3.1 billion after a short-seller called Pera's firm Ubiquiti Networks a "fraud." Short-seller Andrew Left's Citron Research published a report that highlighted seven alleged "red flags" about Ubiquiti. Following this, Pera took to Twitter to address some questions from users about the allegations made by Citron.