Most people in most situations could probably benefit from one tiny prompt: “Are you sure you want to do that?” Fifteen-year-old techie Trisha Prabhu says that question could be the difference between life and death.

Prabhu is the inventor of ReThink, a software program that recognizes when users enter phrases often used to cyberbully into a computer—and displays a pop-up window asking the writer to reconsider. The Chicago high school student’s own studies find that a simple prompt (“Are you sure you want to send that message?”) is enough to discourage its teen users from sending nasty missives a whopping 93 percent of the time.