What anti-cheating measures has FIDE taken at Candidates as Nakamura criticises them?

After American chess Grandmaster Hikaru Nakamura criticised FIDE over its anti-cheating measures at the Candidates Tournament, an official said they use both "covert" and "overt" devices. "The physical scanners are overt devices you can see...We also have covert devices that monitor signals coming into the hall," he stated. The official added that new scanners are being used on the players.