If you want to completely cloak whatever it is you're viewing on your monitor, you can turn it into a private screen that will look blank to everyone else but you. You only need a few materials for this hack.
Because you have to take the monitor apart, however, it's best to use an old one that you're willing to sacrifice. You'll also need either old sunglasses or one of those plastic 3D glasses you get from the movie theatre.
Instructables users dimovi provides the full step-by-step directions, which include cutting out the polarised film on the monitor glass, cleaning off the glass, and hacking the glasses with the polarised film.
You may look crazy to other people, though, if they see you wearing sunglasses indoors staring at a white screen.
Privacy monitor hacked from an old LCD monitor [Instructables]