Secretly taking photos or videos of someone (sneak shot); often implies voyeuristic/illegal filming (tōsatsu).
電車での隠し撮りは犯罪に当たるので絶対にやめてください。
Secretly filming on trains is a crime, so never do it.
芸能人が隠し撮りされてトラブルになった事例が報道された。
There was a report of a celebrity being secretly filmed, which caused trouble.
隠し撮りを見つけたら、すぐに警察に通報するのが安全だ。
If you find a hidden recording, it's safest to report it to the police immediately.