If a biometric system identifies a legitimate user as unauthorized, and denies that user access, it is known as a false rejection. False acceptance on the other hand is when a biometric system authorizes an illegitimate user. FAR is the false acceptance rate—the lower the better. CER stands for crossover error rate, which is the comparison of the FAR and the FRR. False exceptions have to do with software that has failed and needs to be debugged.