In the latest cybersecurity incident to hit US television network Home Box Office (HBO), a hacking group known as "OurMine" breached a number of its social media accounts before leaving a series of messages referencing recent leaks of the studio's content.

"Hi, OurMine are here, we are just testing your security, HBO team please contact us to upgrade the security," one of the updates stated. The same post appeared on two Twitter accounts dedicated to HBO shows Game of Thrones and Last Week Tonight with John Oliver.

In one, the hackers wrote: "let's make #HBOHacked trending". It is unclear how long the accounts were breached, however reports indicate the incident occurred late on Wednesday 16 August. They were quickly removed and none of the posts remain online.

"We are investigating," a HBO spokesperson told The Hollywood Reporter, which reported that the accounts of Veep, Silicon Valley and True Blood were also hit.

While the incident will no doubt cause embarrassment for HBO technology chiefs, the hack targeting the social media accounts is fairly typical of the OurMine group.

In 2016 it infiltrated the accounts of Facebook's Mark Zuckerberg and Google's Sunder Pichai.

The group even had a short-lived feud with whistleblowing platform WikiLeaks. Little is known about the culprits behind the alias, but one of its members previously claimed it was a three-person unit in an interview with Wired last year. It initially described itself as a security company.

It is believed that the OurMine team exploits weak passwords on Twitter accounts to gain entry and then toy with its victims – however it is not known for changing the credentials.

For the past month, a hacker using the pseudonym "Mr White" has been attempting to extort the network for millions of dollars – claiming to have stolen gigabytes of programming material from its computer networks. It has already started leaking some of the content.

That included scripts for unaired episodes of Game of Thrones and full-length episodes from Curb Your Enthusiasm, Ballers, Room 104 and Insecure. HBO attempted to bargain with the culprit, offering $250,000 disguised as a bug bounty to make the leaks come to an end.

HBO's chief executive, Richard Plepler, has remained transparent but previously attempted to play down the scope of the incident, especially in relation to compromised email accounts. "Any intrusion of this nature is obviously disruptive, unsettling, and disturbing," he said.

"I can assure you that our senior leadership and our extraordinary technology team, along with outside experts, are working round the clock to protect our collective interests. The problem before us is unfortunately all too familiar in the world we now find ourselves a part of."

In separate cases, unaired Game of Thrones episodes were also leaked by HBO partners in India and Spain. Despite the bad press, viewership ratings of the show are at an all-time high.