By usb mods,I think you are referring to the fact that you could usb mod things like your clan tag,custom class names etc.The reason you could do it in cod4,waw etc,is that in waw and cod4,your multiplayer progress was stored in the gpd file located within your gamer profile.In more recent cods (black ops,mw3 etc) the info is not stored on your gpd file,meaning you cant edit them.If you are talking about campaign modding,you can find a tut here: Edit:Go to his channel.