The hackers who compromised HBO's network systems in July have threatened to leak the final two episodes of Game of Thrones.

The "Mr. Smith group" of hackers told tech site Mashable that it has access to "many HBO platforms" and that HBO should be "ready" for the leak of episode six and seven of its biggest hit immediately ahead of the show's finale.

The hackers also gave Mashable a list of the usernames and passwords for a number of HBO's social media accounts, including its primary @HBO Twitter account. Last week the OurMine hacking group took control of HBO's social media, including the Game of Thrones Twitter account.

The US TV network has refused to pay a multimillion dollar ransom demand to the hackers, who compromised the network's systems in July and have since leaked a series of embarrassing documents, emails and unaired shows, including Game of Thrones and Curb Your Enthusiasm.

Game of Thrones is already one of the most pirated TV shows of all time. Experts have argued that due to the prevalence of TV show piracy, threats of releasing unaired episodes were not enough to coerce payment.

Alex Heid, chief research officer at risk management firm SecurityScorecard said: "Pirated content ends up on Pirate Bay within 24 hours of airing. Any show on HBO, any movie, the moment it's released, on the first day, you see it on pirated internet streams.

Analysts agree that HBO was aided by the fact that the hackers only released a few shows and that an entire season wasn't released in one go, forcing viewers who wanted to watch it as soon as possible to subscribe to the TV network.

More potentially damaging to HBO could be the release of further sensitive information. Previous dumps listing actors' personal details, scripts, shooting plans and a trove of emails. Up to now the damage caused to HBO by the leaks has paled in comparison to the chaos caused by the hacks on Sony Pictures in 2014.

A person familiar with the situation, speaking on condition of anonymity because they weren't authorized to speak publicly, said HBO was proactive in communicating with the Game of Thrones actors ahead of their personal information being released to the public, which may have helped mitigate the impact of confidential data leaks.

Richard Levick, the head of crisis-management firm Levick, said that being upfront with employees, customers and third parties about cyberattacks is essential. He said: "You can't sweep it under the rug. You can't be opaque about it."