A hacking group has claimed responsibility for the breach of data at entertainment giant HBO, including the script for a Game of Thrones episode.

The group sent out an email to a number of journalists, reportedly saying ‘HBO is falling’ and claiming to have gained access to 1.5 terabytes of data.

HBO confirmed that there had been a ‘cyber incident’ in an email from chairman Richard Plepler, which was then also released to reporters. Plepler stated that the incident ‘resulted in some stolen proprietary information, including some of our programming.’

In response to this, the company stated that it is carrying out an investigation in conjunction with law enforcement. It added that data protection is a ‘top priority’ of the organisation.

On the financial impact of the leak for HBO, vice president of technology at BeyondTrust, Morey J. Haber, commented: ‘The monetisation of damage is very different than a traditional breach against a bank or healthcare organisation.

‘For HBO, it is a black eye but one that will heal fast. The highest monetisation problem will be fixing any security holes that lead to the leak so that this does not happen again. If it became a recurring problem, other forces like brand reputation and regulatory oversight might come into play.’

As well as the Game of Thrones script, the hacking group has apparently put upcoming episodes of Ballers and Room 104 online, though HBO has made no comment on the specific content that has gone missing.

Senior director at BeyondTrust, Brian Chappell, believes the cause is likely to be ‘either an exploit to a well-known vulnerability or a user with excessive privileges who fell for a phishing attack.’ As such, he argues that HBO should review its management of vulnerabilities and privileged account systems.

In the email to reporters, the hackers promised that more leaks would be revealed. It is not the first time HBO has had scripts leaked, with the first four episodes of the fifth series distributed by advance screeners, such as members of the press.

However, HBO’s Plepler was defiant, saying: ‘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.’