After anonymous hackers claimed to have leaked the script of the next episode, season 7 episode 4, of the popular TV show Game of Thrones, TV network HBO started investigating the data breach.

A statement released earlier in the day said, "HBO recently experienced a cyber incident, which resulted in the compromise of proprietary information. 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."

Hackers claimed to have stolen 1.5TB of data, including the script for the fourth episode of the current season of Game of Thrones, as well as unreleased episodes of  Ballers and Room 104 - two of the network's other shows. There are four episodes remaining in season seven of Game of Thrones, with the finale scheduled for August 27. 

In an email sent to a popular online website, the hackers claimed that "the greatest leak of cyber space era" was happening, and invited the website's users to download the leaked script. The anonymous hackers also threatened to leak out more material in the near future.

"Any intrusion of this nature is obviously disruptive, unsettling, and disturbing for all of us," HBO CEO Richard Pepler was quoted as saying. "The problem before us is, unfortunately, all too familiar in the world we now find ourselves a part of," he added.

The network has not commented on what specific content the hackers may have acquired.

HBO has previously battled with Game of Thrones leaks though not necessarily because of hacking. In 2015, the first four episodes of season five were leaked online prior to the season premiere.

Back in April, video streaming service Netflix was hacked and episodes of Orange Is the New Black season five were released online prior to its debut. A hacking group called the 'Dark Overlord' had claimed responsibility for that hack.