HBO has suffered a data breach that has resulted in previously unreleased episodes and information from its lineup of shows, including a “Game of Thrones,” Season 7 leak being published online, Entertainment Weekly reported. Additional information may also have been stolen that has yet to be revealed, a cybersecurity expert told International Business Times.

Hackers claimed to have obtained at least 1.5 terabytes of data from the company in the breach. Some of the stolen information, including upcoming episodes of “Ballers” and “Room 104,” have been posted online.

Read: ‘Game Of Thrones’ Season 7 Spoilers: A Return From The Dead, Surprise Attack Confirmed By Reddit?

The attackers who targeted HBO have also published a script that is allegedly "Game of Thrones" Season 7 episode 4, which is set to air next Sunday. The group has promised more content will be posted in the days to come.

HBO confirmed the "Game of Thrones" Season 7 hack in a statement to Entertainment Weekly. “HBO recently experienced a cyber incident, which resulted in the compromise of proprietary information,” a spokesperson for the network said.

“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.”

The company also confirmed the breach in an internal email sent from HBO chairman and CEO Richard Plepler to the company’s employees. In the email, Plepler confirms the network had “proprietary information, including some of our programming” stolen in the data breach. Plepler went on to call the attack “disruptive, unsettling and disturbing."

Read: Disney Hacked: New 'Pirates of the Caribbean' Movie Reportedly Held For Ransom

The breach first came to light Sunday evening, when the apparent hackers who carried out the attack sent out an email to a number of reporters touting the stolen material and offering an interview for those who “spread the story well.”

“Hi to all mankind,” the email read. “The greatest leak of cyber space era is happening. What’s its name? Oh I forget to tell. Its HBO and Game of Thrones……!!!!!! You are lucky to be the first pioneers to witness and download the leak. Enjoy it & spread the words. Whoever spreads well, we will have an interview with him. HBO is falling.”

Jon Snow, "Game of Thrones" S7E2 Jon (Kit Harington) faces potential revolt in the North on Season 7, Episode 2 of “Game of Thrones.” Photo: HBO

HBO has not confirmed if any full episodes of its massively successful show “Game of Thrones” were stolen in the breach. While the hackers have promised more information will be published, they did not note if any full episodes were stolen.

Terry Ray, CTO of cybersecurity firm Imperva, told IBT the fact the breach was brought to light by the hackers suggests it’s possible more information could have been stolen that has not yet been disclosed.

“We don’t know how long they have been accessing the HBO system or what additional data—financial, email, employee info—the attackers may have in addition to the episodes and scripts," he said.  

Ray said most organizations will get hacked at some point and need to take proactive steps to identify and secure sensitive data, be it financial, intellectual property or anything in between.

"Businesses can invest in solutions that help them pinpoint critical anomalies that indicate misuse of enterprise data stored in databases and file servers, and that also helps them to quickly quarantine risky users to prevent and contain data breaches proactively,” he said.

The HBO breach comes just months after a number of other high-profile hacks resulted in the theft and publishing of a number of shows and films. Prior attacks have primarily been attributed to a group known as TheDarkOverlord. The anonymous hacking group has not been directly linked to the HBO breach.

TheDarkOverlord first claimed in April to have content from a number of networks, including ABC, CBS, IFC, FOX and National Geographic. That same month, the group released episodes of Season 5 of the Netflix original series “Orange is the New Black.” In June, the group published footage online of the unreleased ABC show “Steve Harvey’s Funderdome.”

While TheDarkOverlord made good on its threats to Netflix and ABC, the hacking group has been less than consistent in its behavior. In May, Disney CEO Bob Iger told a company town hall meeting that Disney was being threatened with the release of “Pirates of the Caribbean: Dead Men Tell No Tales” if it did not pay a ransom.

TheDarkOverlord took credit for the threat and said it planned to release the film in chunks ahead of it being available in theaters. However, the hacker group never made good on its threat and Iger later said, “To our knowledge we were not hacked.”

Richard Stiennon, Chief Strategy Officer at Blancco Technology Group told IBT content producers are increasingly becoming targets of hacks and need to take steps to secure their systems to ensure their content isn't stolen and leaked.

"Ever since the infamous attack on Sony Pictures, there is evidently an appreciation on the part of hackers for stealing high value content such as movies and TV shows," Stiennon said. "Final production videos are a class of information and the theft of such information poses extraordinary losses, if stolen. Content producers and all the parties involved in shooting, editing and post-production processing and distribution should be on high alert."