HBO said it was the victim of a hack that may have leaked as much as 1.5 terabytes of show data, including a script to an upcoming episode of Game of Thrones.

"HBO recently experienced a cyber incident, which resulted in the compromise of proprietary information," the network said in a statement sent to Entertainment Weekly, which broke the news of the breach. "We immediately began investigating the incident and are working with law enforcement and outside cybersecurity firms. Data protection is a top priority at HBO, and we take seriously our responsibility to protect the data we hold."

EW said unidentified hackers claimed to have obtained one upcoming episode each of Ballers and Room 104. The videos "have apparently been put online," the publication said without elaborating. According to EW, the leaked contents also include a script for next week's fourth episode of Game of Thrones. So far, Ars is unable to confirm any of the leaked material. The HBO statement didn't detail any of the proprietary information that was taken.

HBO has fought hard to prevent storylines from GoT from leaking. In 2015, the first four episodes to the show's fifth season became available on torrent sites before being aired on the network. HBO said the leaked episodes originated from a group HBO had approved to receive them. The network has since stopped sending episodes to press and industry insiders in advance of their airing. HBO has also worked to prevent storylines from becoming public in advance. So far, there are no reports the leaked GoT script is currently available online.

In a memo distributed to HBO employees CEO Richard Plepler said senior executives, working with outside security experts, are "working round the clock to protect our collective interests."