Clicker training, shutting him out of the room, air cans on the desk facing the monitor, or sticky tape can help. The latter two typically only need to be used until kitty “gets it,” then can be removed (though may occasionally require “retraining.”

It also helps if kitty has a place on or very near the desk that it his, such as a bed or cat tree. My boyfriend literally has another computer chair right next to him just for the cats so they don’t walk all over his keyboard.

Sometimes it takes this plus one of the methods above to truly kick the habit