Hackers have targeted HBO in a major cyberattack, stealing unaired episodes from a variety of shows and leaking at least one alleged script from the popular fantasy show “Game of Thrones,” according to multiple reports.

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In a statement released Monday, network officials confirmed that “proprietary information” was compromised in a cyberattack.

“We immediately began investigating the incident and are working with law enforcement and outside cybersecurity firms,” the statement said. “Data protection is a top priority at HBO, and we take seriously our responsibility to protect the data we hold.”

Entertainment Weekly reported that several unaired episodes of HBO shows were put online, as well as what appeared to be at least one script or treatment from the popular "Game of Thrones" series. The script is purported to be for episode four of the current season of the show, which is scheduled to air Aug. 6, The Telegraph reported.

Unreleased episodes of “Ballers” and “Room 104” also appeared online, according to the newspaper.

Hackers claimed to have stolen 1.5 terabytes of data from HBO, EW reported.

It was not immediately clear who was behind the attack.

It's not the first time HBO has dealt with unauthorized copies of its shows' episodes appearing on the internet. In 2015, several unaired episodes of "Game of Thrones" appeared online ahead of the premiere of the fantasy show's fifth season. The leak happened after HBO mailed DVD copies of the episodes to members of the media for review, according to Forbes. The news site reported that HBO stopped using sent DVDs and switched to a secure streaming site to prevent similar leaks.

"Game of Thrones" has been the most popular show to pirate since 2012, according to TorrentFreak.com.

HBO is not the first entertainment company to fall victim to cyberattacks. Sony Pictures was hacked in 2014 by a group who was believed to be backed by North Korea. The group released a slew of emails and unreleased films.

Larson Studios, a small postproduction services company, was hacked in late 2016. The breach resulted in several episodes of the popular Netflix show "Orange is the New Black" appearing on torrent sites for download before their official release, The New York Times reported.