Shailene admits she has always been suspicious about iPhones and other personal devices, and when Snowden released the NSA information she felt validated to have had initial concerns.

"The first time I got an iPhone, I was 18 and I thought they were going to record stuff and people can see through this camera," she tells WENN. "When Ed released the information that he disclosed, it hit me with a certain gravitas of, 'This is real!' and was validated as more than a suspicion.

"When I heard that Oliver Stone was making this movie I wrote him a letter. It was a thank you for making a movie like this because the power of storytelling in Hollywood, whether you're displaying information that's true or false, you're hitting all the senses to learn. So for someone to take a story like the Edward Snowden story, where half the people know who he is and half the people have never heard his name before; half have strong opinions that he's a traitor and the other half think he's a hero... is a big deal."

"Everyone has such strong opinions of a man we actually know nothing about," she adds. "We are quick to judge in our society but so often we are often fed one narrative. With Snowden, we were only fed the narrative through mainstream media and independent journalists. We never had the luxury of the historical events that led him to do what he did."

And portraying his girlfriend Lindsay Mills has given Woodley a new perspective: "My judgements now have shifted a little bit because I understand the back story and there's a certain sense of empathy that I do have for him."

Snowden, starring Joseph Gordon-Levitt as the whistleblower, hits cinemas later this month (Sep16).