For the third consecutive year, HBO's heroic fantasy production is the most illegally downloaded series worldwide in 2014, just ahead of "The Walking Dead" and "The Big Bang Theory."

According to estimates from Torrentfreak.com, each "Game of Thrones" episode aired in 2014 was pirated 8.1 million times on average. This figure, which does not include illegal streaming views, continues to grow with each passing year. In 2013, the series saw 5.9 million illegal downloads per episode.

"Game of Thrones" remains phenomenally popular, including among video pirates, with a wide lead over runner-up "The Walking Dead." AMC's zombie drama saw 4.8 million downloads per episode in 2014, compared to 3.6 during the previous year. Episodes of the most watched comedy in the US, "The Big Bang Theory," were illegally downloaded 3.9 million times this year on average, which is around 500,000 more than in 2013.

"How I Met Your Mother" has also been subject to wide-scale pirating this year, with around 3.5 million clicks per episode. Hot on the heels of the now departed comedy is "Gotham," the only new series in the ranking, with around 3.2 million unauthorized downloads per episode.

"Arrow" soared from tenth to sixth place this year, with 2.9 million pirated downloads per episode. "Grey's Anatomy" (2.8 million), "Vikings" (2.7 million), "Suits" (2.5 million) and "South Park" (2.4 million) round out the ranking.