New documentary The Great Hack explores the Cambridge Analytica/Facebook scandal, which saw data harvested from people's profiles without their consent and then used to target them with political advertising. Laura Harding meets the filmmakers who are convinced this story is just the beginning of a dark kind of data war.

Have you ever wondered if your phone is listening to you?

Have you talked about something and then noticed you are seeing ads and articles about it popping up on your screen?

That is the creepy question that opens The Great Hack, a chilling new documentary about the dark world of data exploitation.

The film centres on the scandal that erupted after it was revealed that British political consulting firm Cambridge Analytica had harvested the personal data of millions of people's Facebook profiles without their consent and used it for political advertising purposes, including the Brexit referendum and the US election.

"What Facebook did should be seen as the largest corporate negligence case in modern history, where on their watch they allowed for people's data to be used unethically," says the film's co-director Karim Amer.

"They allowed people to be experimented on by weapons-grade information campaigns on a military level and allowed for a breach where millions of people have had their data completely taken and will never come back.

"This is like red alert, the system has been attacked and doesn't really work any more, this is a structural problem.

"It isn't even about Leave vs Remain, it's much bigger, it goes to the core of how do you have a society of shared and common values when everybody is living in a polarised reality of their design? That is a much bigger question."

He pauses.

"People think their phone is listening and that feeling is universal, around the planet.

"But phones, from the evidence we have seen, are not listening in on you, but the reason you feel that way is because the algorithm's predictability does work.

"It means you are persuadable. Whether you like it or not, you are."

This doesn't necessarily mean politically persuadable, about hot button issues such as Brexit here in the UK, or gun control in the US, but in other areas.

"I think that is what we hope the film can give a window into, this moment in time when we realised how the balance of power between us and technology has shifted," he adds.

It wasn't always this way, There was a time when Facebook felt harmless, even helpful, co-director Jehane Noujaim says.

"We come from Egypt where these tools were used as a powerful tool for change, for holding government accountable, for gathering people, for giving people a voice."

Noujaim was arrested during the Egyptian revolution in 2011 and social media was instrumental in getting her released.

"One of the things that happens is that there is an attempt by the government to make it very difficult for family members to find you. The harder that you make it for people to go down into the street or to protest or to express themselves, the easier you are able to control the population.

"So they try to basically disappear you when you get arrested. I was found when a lawyer that knew me tweeted my photograph out and somebody found me in one of the prisons.

"These really were very practical tools for what was happening in 2011 and we watched as these tools were celebrated by people who were on the streets, but also by Silicon Valley.

"They were saying, 'We are bringing democracy, these are our tools for change' and then we watched as the pendulum swung in the other direction and these tools, a couple of years later, are being used to manipulate, being used by fascist governments, being used to control, being used to spy on.

"And yet there doesn't seem to be that same taking responsibility for it. It's like that saying: success has a million parents and failure is an orphan."

The film was originally conceived as a documentary about the hack of the film studio Sony Pictures, which included emails between employees, information about executive salaries at the company and copies of unreleased films, but it swiftly turned into something even bigger and even darker.

"We started to see that the much more fascinating hack was the hack of our brains," Noujaim says.

Do you know 5,000 things about yourself? Cambridge Analytica claimed to have had 5,000 data points on every voter. "And that figure is already outdated," Amer points out.

"As David Carroll (one of the film's subjects) says, by the time his daughter grows up she's going to have 80,000 data points about her, over which she has no control or rights.

"Is that OK? What if it's used for malicious purposes and what if it's used for unintended purposes? What have we signed up for when we sign these contracts every day?

"Just because something wasn't illegal, doesn't mean that it's not a crime.

"That particularly applies in the area of technology and society because the technology platforms have usurped our legal mechanisms."

Watching the film, it's hard not to immediately want to delete your profile.

"That has been one of the biggest reactions," he laughs, "but it was not our intention, we are not calling for it.

"We are still on Facebook, because I think we see it as a false choice, give up all your connectivity to demand privacy? No, I think the admission fee to the connected world shouldn't be giving up all your privacy.

"We shouldn't have to say no connectivity because of that, it's on them to fix it.

"We didn't do anything wrong, they did.

"We have always needed technology to expand the capacity and possibility of what we can achieve as a society but at the same time we need ethics to preserve our humanity.

"We are not calling for Delete Facebook, we are not calling for a Luddite revolution, we are just calling for a way in which we can have ethics and tech co-exist.

"If we do see this moment as a moment to write a new social contract, we should perhaps realise that contract is no longer between citizens and government but between citizens, government and technology platforms, and that social contract might actually be our user agreement."

The Great Hack is available on Netflix.