Operation Firestorm Breakthrough : Bright Group

Hi DeadsideHabibiYT​,

Ruxem is correct, this is someone using anonymous mode, where the game is assigning a random username (this is also why you can't find them). There's also a Streamer mode setting that will do the same to everyone else. The names the game assigns usually begin with "Bright" or "Any", but there may be more variations out there. 

The best thing to do when you encounter someone you suspect is cheating, is to report them through the scoreboard.