The 19-year-old actress, who plays noblewoman turned assassin Arya Stark in the hit HBO fantasy series, is furious that details from the scripts have reportedly appeared online.
"It really, really upsets me," she tells Britain's Radio Times magazine. "Because, there's only a certain group of people who'd look at that anyway, compared to the audience that watches the show.
"It hurts. It's just like, oh we wanted to tell this story, and yeah, lots of people don't want to read it, and don't want to look at it."
One major alleged leak occurred in November last year (16), when extremely detailed plot points tallying with on-set photos appeared on the social media site Reddit.
And Maisie says that what particularly upsets her about the leaks is the thought that it may be coming from one of the cast or crew.
"But then it's even more annoying when you know (the leaks) might be from someone on the inside, and it's just like... you're trying to make something really cool, that is really cool, and people really like, and it's like 'stop ruining it'. It's such a childish, annoying thing to do. And yeah, it's sad. It really annoys me."
With Game Of Thrones set to come to an end next year (18) after eight riveting series, Maisie is now looking to her future, although she might not continue pursuing an acting career.
"I'm excited because it (the show ending) means I can do absolutely anything I want," she explains. "I could go away for three years and...travel the world, or I could write a film... I could do anything, and it's quite exciting."
Game of Thrones' seventh season begins in April (17).