London: After anonymous hackers claiming to have leaked the script of the next episode of "Game of Thrones" (GoT) along with 1.5TB of data, popular TV network HBO was investigating the data breach. "HBO recently experienced a cyber incident, which resulted in the compromise of proprietary information," Sky News quoted HBO as saying late on Monday. "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," HBO added in a statement. According to the Telegraph, hackers claimed to have stolen 1.5TB of data, including the script for Season 7 Episode 4 of 'GoT' as well as unreleased episodes of 'Ballers' and 'Room 104' -- two of HBO's other shows. There are four remaining episodes in "Game of Thrones" Season 7, with the finale scheduled on August 27. In an email sent to Entertainment Weekly, the hackers said: "Hi to all mankind. 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," the email further read. 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. As has been the case with any challenge we have ever faced, I have absolutely no doubt that we will navigate our way through this successfully," he added. The network has not commented on what specific content the hackers may have acquired. According to Ankush Johar, Director of BugsBounty.com, "After Sony's hack in 2014, the HBO hack is a reminder of the new world that we live in. 1.5TB is a lot of data to lose." "To have lost 1.5 Terabytes of data would have taken time. It could have been mitigated, if the alarm systems were in place, so the damage could have been minimised," Johar said in a statement on Tuesday. "The question is not IF you will be hacked, it's WHEN you will be hacked. And when you do, have you put the right alarm bells in place to mitigate your risk and minimise the damage?" Johar added. According to a report in The Verge, 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.