Facebook on Monday said it's hired the digital forensics firm Stroz Friedberg to conduct a "comprehensive audit[1]" of Cambridge Analytica, the analytics firm that used information from 50 million Facebook profiles -- without permission -- to help Donald Trump's 2016 presidential campaign.

Facebook said it first learned of the misused data in 2015, and by August 2016[2] the company had asked Cambridge Analytica to certify that it had deleted the data. Facebook put in the same request with Aleksandr Kogan, the researcher who developed the personality prediction "research" app that collected the data. Although Facebook said it received assurances that the data had been deleted, the company did not verify the responses.

"If this data still exists, it would be a grave violation of Facebook's policies and an unacceptable violation of trust and the commitments these groups made," Facebook's Monday blog post said.

Cambridge Analytica has agreed to comply with the audit, Facebook said, and will give Stroz Friedberg "complete access" to their servers and systems. Facebook said Kogan has also verbally agreed to an audit. However, whistleblower Christopher Wylie has thus far declined to do so, Facebook said. Wylie, a former employee of Cambridge Analytica's parent company SCL, developed the programming used to exploit the Facebook data in question.

Facebook announced late Friday[3] that SCL and Cambridge Analytica were suspended from the social network. The company failed to disclose the abuse of users' data until the story exploded over this past weekend. However, Facebook said Monday, "We remain committed to vigorously enforcing our policies to protect people's information."

The company also said that it has since adopted a "robust" review process for apps that ask for certain information from users. "We actually reject

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