The CEO added that Facebook could only record audio as part of a video that's being filmed and uploaded by users.
It comes in the wake of revelations last month that millions of users' personal information was wrongly harvested from the website by Cambridge Analytica, a political consultancy that has counted US President Donald Trump's election campaign among its clients.
Mr Zuckerberg said that the company tracks non-users for "security purposes", without elaborating.
But he stiffly defended Facebook's use of the data and postings of the 2.2 billion users of its free platform - in order to attract the ad revenue that the $480- billion company depends on.
Facebook's share price rose by more than 5% on the first day of Zuckerberg's testimony boosting the tech company's market value by more than $24 billion.
"Every time that someone chooses to share something on Facebook. there is a control".
As many as 87 million Facebook users who might have had their data shared were to receive a detailed message on their feeds this week. Some researchers won't even have access to it unless they are physically in Facebook's headquarters in Menlo Park, California, he said.
He told me that Dr Kogan's work had raised issues for the university: "Even if an academic does something - quote unquote in their "spare time", with their own company - they still ought to be held to professional standards as a psychologist". Arguably, many of those products, from medicine to fuel, potentially put more Americans at greater risk than Facebook does.
Several Republicans also strongly voiced their concerns on the opposite end of the spectrum - that over-regulating or policing of the platform would lead to anti-conservative bias and a general silencing of offensive opinions. It has also asked for details on how Facebook users in the country were affected by the Cambridge Analytica scandal.
"We have communicated directly with Diamond and Silk about this issue".
"Nothing is unsafe about that", Zuckerberg replied, explaining that these were mistakes.
Facebook has a 200-member counter-terrorism team to deal with objectionable and terrorist content.
You can find out if you were one of the people who had their data taken, by clicking here.
"It's pretty obvious to me that someone is listening to the audio on our phones", Buschon said.
When he was asked by Graham whether Facebook would submit to regulation, Zuckerberg told him he would if it were the right kind of regulation.
"That goes for fake news, for interference in elections and we didn't take a broad enough view of our responsibility and that was a big mistake and it was my mistake and I'm sorry", the Facebook CEO said.
The company has always denied these allegations.
IBM stops advertising on Laura Ingraham's show MORE testified in back-to-back hearings before Congress on the incident and faced a number of questions on privacy and data sharing practices at Facebook. But he warned that lawmakers should be careful in what they propose.
The company does this by using different techniques integrated into pages around the web. A few lawmakers argued that Facebook doesn't have a true competitor - overall a much more informative hearing.