Facebook CEO Mark Zuckerberg has fronted US Congress about the social media site’s data usage controversy.

Mr Zuckerberg opened his testimony with a public apology, taking full responsibility for failing to prevent Cambridge Analytica from obtaining data from users.

A key discussion in the five-hour hearing was the urban legend that Facebook secretly records audio through microphones on a phone to target advertisements to users.

Does Facebook tap your microphone?

The social media site says it does not tap your microphone.

Senate Gary Peters asked Mr Zuckerberg the direct question of “Yes or no, does Facebook use audio obtained from mobile devices to enrich personal information about users?”

He replied with a no, saying the company only has access to an individual’s audio when people record videos on the social media platform.

“To be clear, we do allow people to take videos on their devices and share those, and videos have audio, so we do while you’re taking a video, record that and use that to make the service is better by making sure your videos have audio,” Mr Zuckerberg said.

An estimated one in 50 Australian Facebook users are thought to have their data leaked. Photo: Getty

What else was discussed in the hearing?

• Why the company waited more than a year to act on the privacy breach
• Mr Zuckerberg’s response to Russian meddling
• Facebook’s handling of the media
• Mr Zuckerberg’s claim that his company is developing artificial intelligence to scan for suspicious activity
• The site targeting users by race for advertisements
• The company allegedly censoring content from conservative organisations
• The senators threat that they may enforce privacy rules if the site can’t regulate itself
• Other social media sites that users could use if they are not satisfied with Facebook