Secret Photography
Secret Filming
noun, verbal noun
Stealing photographs of you. Wait, you didn't know you were being photographed / filmed? That's secret photography or secret filming Creeeeeepy.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
電車内で居眠りしているところを盗撮されたんです。
Photos were taken of me in secret while I was napping on the train.