Need some thorny security hedge or bush
I'm with GC on the plant suggestions. You might also consider some of the chinese hollies, the ones with the sharp spines. They will grow close to the house and dense and can be trimmed (if you must). Just depends on whether you want high or low, dense or open, etc.
However, can you not secure the window? Not that there's anything wrong with planting, but that would be my first choice.
If it's worth doing, it's worth doing right. If you wouldn't put your name on it, it ain't done right!