The data scientist at the heart of the Cambridge Analytica scandal, Aleksandr Kogan, has apologised for his role in it.

Kogan spoke to 60 Minuteson Sunday, maintaining that at the time, he believed he was doing everything correctly, and that he wouldn't have done anything to destroy his relationship with Facebook.

But Kogan apologised for thinking that people knew they were giving away their data.

"Back then we thought it was fine. Right now my opinion has really been changed," he told the program.

"And it's been changed in particular, because I think that core idea that we had — that everybody knows and nobody cares — was fundamentally flawed. And so if that idea is wrong, then what we did was not right and was not wise. And for that, I'm sincerely sorry."

Facebook has since expressed remorse, taking out full-page ads to say sorry too back in April. Mark Zuckerberg also said sorry in Congress.

Of course, things weren't so contrite amid revelations of the scandal, when the social media giant said Kogan "lied" to them. He said Facebook allowed it to happen, because it "clearly has never cared" nor enforced its developer policy.

Kogan's app had a terms of service which allowed transfer or sale of user data, despite it being in conflict with Facebook policy.

"And they tell you that they can monitor it. And they can audit. And can let you know if you do anything wrong. I had a terms of service that was up there for a year and a half that said I could transfer and sell the data. Never heard a word [from Facebook]," he said.

"The belief in Silicon Valley and certainly our belief at that point was that the general public must be aware that their data is being sold and shared and used to advertise to them. And nobody cares."

Kogan maintained he was being singled out by Facebook, even though he believes the problem is much bigger. He pointed to a former colleague, Joseph Chancellor, who now works for Facebook but said they "did everything together" for the Cambridge Analytica project and has escaped blame.

Facebook even worked with Kogan between 2013 and 2015, where he said he was brought in to teach staff about what he learnt from the data he collected from Cambridge Analytica.

Facebook confirmed to 60 Minutesthat he did some "research and consulting" work with them, but wasn't aware of Kogan's Cambridge Analytica activities.