Augmented reality (AR) technologies -- which overlay digitally generated information on a user's perception of the physical world -- are at the cusp of commercial viability, appearing in platforms like Microsoft HoloLens, Magic Leap, Meta, and automotive windshields. Though these technologies offer great potential benefits, they also raise new and serious computer security and privacy risks. This project focuses on investigating and addressing security and privacy issues due to the virtual output (visual, audio, or haptic feedback) that AR applications generate.