looking over someone's shoulder
肩越しに画面を覗かれた。
Someone peeked at my screen over my shoulder.
後ろから肩越しにメモを見てきた。
They looked at my notes over my shoulder from behind.
列に並んでいる間も肩越しにスマホを操作された。
Even while I was in line, someone reached over my shoulder to operate my phone.