Remember, light travels in a straight line. Unless you have something hovering in front of a bare window, their field of view becomes limited depending on the entry angle.

On a positive note, all one needs to defend if such a device came to use, is find its wavelength, and either match it as a jamming device (a small countermeasure mounted pointing toward the window), or stop the light in its tracks by applying a tint like film which absorbs it.

For neat little experiment you can try with a dollar store pointer, you can make a listening device. Its a fun project..

All you need is about 3$ in parts and a laptop. Soldering iron recommended, but not 100% necessary if you dont have one.