In this contribution, we study the different stellar configurations that can produce signals resembling those produced by a transiting planet. We list several strategies to recognize these false alarms. For the most common configurations, we delineate which of these strategies are able to detect them. The case of an eclipsing binary of similar components, whose light is diluted by a third star, is discussed in some detail. Multicolor photometry is considered as a useful tool to recognize this common case. Two example of false alarms obtained by the STARE project, the different techniques used to study them, and the most probable configurations producing them are shown.