Manifestation of corrupted code that the World Machine makes. Blocks many areas in the game. During the solstice path, Squares are far more prevalent due to the World Machine not having the protocol for the path.
Squares may have the ability to incapacitate or even kill people, however with robots (including Silver) they are still able to speak in a more garbled state.
Hopefully that's a good starting point ☜(■_■☜)