Optically controllable windows and an associated window control system provide a building security platform. A window controller or other processing device can monitor for window breakage, cameras associated with windows can monitor for intruders, and transparent displays can provide alerts regarding detected activity within a building. A window control system can detect deviations from expected I/V characteristics of an optically controllable window during normal operation of the window (tint transitions, steady state conditions, etc.) and/or during application of a security-related perturbing event, and provide alerts upon their occurrence.