Tempest in a Teapot: Compromising Reflections Revisited

Reflecting objects such as tea pots and glasses, but also diffusely reflecting objects such as a user´s shirt, can be used to spy on confidential data displayed on a monitor. First, we show how reflections in the user´s eye can be exploited for spying on confidential data. Second, we investigate to what extent monitor images can be reconstructed from the diffuse reflections on a wall or the user´s clothes, and provide information-theoretic bounds limiting this type of attack. Third, we evaluate the effectiveness of several countermeasures. This substantially improves previous work (Backes et al., IEEE Symposium on Security & Privacy, 2008).