"What you're talking about is a conspiracy theory which gets passed around that says we listen through the microphones and record audio to target ads", Zuckerberg said.
Zuckerberg, who at 33 runs a multi-billion-dollar company with some two billion users, accepted personal responsibility for the leak of users´ data and vowed that the company will do better in guarding such information.
"This is a serious matter, and I think people expect us to take action", Cornyn told reporters after his speech. He said the firm is now complying with a full audit of its records, after it was reported last monthCambridge Analytica still had access to its harvested data. "I've never consented to having Facebook collect my data, which can be used to draw very detailed inferences about my life, my habits, and my relationships".
Numerous Senators on the panel did, however, question whether users were giving informed consent; in other words, whether they knew what they were agreeing to.
The roll out of the notification will happen over time, but users can now check to see if they were affected via a dedicated link.
Senator Lindsey Graham from SC asked Zuckerberg to name his company's biggest competitor.
"We didn't take a broad enough view of our responsibility, and that was a big mistake", said Zuckerberg.
But he added: "Our work with the special counsel is confidential and I want to make sure that in an open session I'm not revealing something that's confidential".
The revelations prompted a number of global investigations. The company is accused of using that data to influence the 2016 elections. Have questions about Facebook?
On Wednesday, the Facebook boss will testify before the House Energy and Commerce Committee, in a hearing dubbed "Facebook: Transparency and Use of Consumer Data". "The limits of your right to privacy", said Sen.