Collusion is a major unsolved security problem in online bridge: by illicitly exchanging card informa- tion over the telephone, instant messenger or the like, cheaters can gain huge advantages over honest play- ers. It is very hard if not impossible to prevent collu- sion from happening. Instead, we motivate an AI-based detection approach and discuss its challenges. We chal- lenge the AI community to create automated methods for detecting collusive traces left in game records with an accuracy that can be achieved by human masters.