kent. reporter: tonight, mark zuckerberg promising to hire thousands of more people to verify political ads so users can see where they come from and who is paying for them. facebook forcing users with big followings to verify their identities, saying they will make it harder for anyone to do with what russians did during the 2016 election. i don t believe today s actions by facebook will completely stop what the russians did in 2016 and what they re planning on doing in 2018. that s a good step in the right direction. reporter: in an exclusive interview with savannah guthrie on today, facebook s second in command, cheryl sendberg apsher apologized for the cambridge analytica scandal. we got multiple assurances from them that the data had been deleted. now, we should have done the forensic audit we re doing now then for sure. reporter: she says facebook is likely to find more problems. but you have an opt-out button.