FACEBOOK chief executive Mark Zuckerberg is set to give evidence to US law-makers about the company’s ongoing data privacy scandal and how it failed to guard against other abuses of its service.

As Zuckerberg prepared for two days of testimony to Congress, his company announced technical changes intended to address privacy issues.

Facebook is beginning to alert the 87 million users whose private data may have been compromised in the Cambridge Analytica scandal. It said most of the affected users are in the US, though there are more than a million each in the Philippines, Indonesia and the UK.

All 2.2 billion Facebook users will receive a notice titled “Protecting Your Information” with a link to see what apps they use and what information they have shared.

Zuckerberg acknowledged that he made a “huge mistake” in failing to take a broad view of his company’s responsibility is in the world.

Cambridge Analytica whistleblower Christopher Wylie previously estimated that more than 50 million people were compromised by a personality quiz that collected data from users and their friends. Recently he said the true number could be even larger than 87 million.

Meanwhile Apple co-founder Steve Wozniak says he is shutting down his Facebook account. In an email to a daily newspaper Wozniak said “Apple makes money off of good products, not off of you”.