Twitter whistleblower: what questions will Peiter Zatko face from lawmakers?

Here are some questions that Zatko might face on Tuesday.

He is likely to be asked about several claims, including that Twitter mishandled user email addresses and phone numbers, that more than 50% of its 500,000 data centre servers are running software that is out of date or has other known security problems, and that employees were found to be installing spyware on their work computers at the request of external organisations.

Nonetheless, Zatko has considerable pedigree, having made his name as an ethical hacker who helped organisations identify flaws in their systems before going on to work in senior positions at Google, the payments firm Stripe and the US Department of Defense. This long track record, and a reputation for professional rigour, led the then Twitter chief executive, Jack Dorsey, to hire him.