Episodes of the latest series of Game of Thrones appeared online after a likely security weakness in the supply chain, according to the security vendor Tripwire.
Copies of the fantasy series appeared on a range of torrent sites on Sunday, in what has been put down to a leak from the press or a studio involved in making it.
Ken Westin, senior security analyst at Tripwire, said: "After the Sony breach many are wondering if HBO may have been hacked and believe that could be the source of the leaked episodes.
"However, I believe this is not a traditional hack where HBO’s network was compromised, but an example of supply chain security in relation to data."
As well as highlighting the the multiple partnerships that are involved in making television shows and films, Westin also noted that "screeners" released as marketing material could also be responsible for the early release of the show, currently in its fifth season.
"These screeners are watermarked and require a legal agreement not to share the material, however these watermarks can be found and blurred so they cannot be identified when movies are then leaked," he said.
Since its launch in 2011 Game of Thrones has been prolifically pirated, with the filesharing blog TorrentFreak judging it to be the most widely shared show for the last three years running.
This year its creator HBO even attempted to release it simultaneously in as many countries as possible to curb piracy, with the launch taking place on Monday in 170 states.
"In many respects the same risks that a movie may go through mirrors that of customer data or other forms of intellectual property, where multiple parties may use the data and it can be passed around and accessed by many different parties," Westin said.
"The more demand there is for a given type of data and the more people involved who have access to it the more likely it is to be compromised by a trusted insider."