Security researcher Sarah Jamie Lewis told Ars that “it’s a pretty reasonable assumption” that at one point the FBI was running roughly half of the known child porn sites hosted on Tor-hidden servers. Lewis runs OnionScan, an ongoing bot-driven analysis of the Tor-hidden darknet. Her research began in April 2016, and it shows that as of August 2016, there were 29 unique child porn related sites on Tor-hidden servers.