Finally, about 18% of requests involved Microsoft handing over no data at all, said the report, either because there was no data to be found or the request was not submitted properly.

BBC: Microsoft details global police data requests

"They've only got data on this final slice of the process, but they are still missing crucial parts of the criminal-justice process, " said Sonja Starr, a law professor at the University of Michigan, who has analyzed sentencing and arrest data and found no marked increase in racial disparity since 2005.

WSJ: Wide Racial Divide in Sentencing

Facebook has revealed it was the target of a "sophisticated attack" by hackers last month, but found no evidence any user data had been compromised.

BBC: Facebook was targeted by 'sophisticated' hackers