there are some genuine "backups" out there but then a copy not matter how good it is is never 100% safe. Wave 4 games are playable and ixtreme have released ixtreme 1.61 for a couple of drives and for the others there is an activate .iso disc that you burn to one layer of a dvd+r dl disc, put it in your drive and select play dvd, once that starts up you press the xbox button on your control pad, eject and insert the game disc.
the activate iso contains the wave 4 information needed to play the wave 4 game.