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).