In this paper, we propose the scattered byzantine failure model. In this model, processes alternate correct and faulty periods. Specifically, during its faulty periods, a process behaves arbitrarily (one cannot expect anything from it during these periods) whereas during its correct periods, it behaves according to its specification. In that sense, the scattered byzantine failure model generalizes the classical Byzantine failure model. We characterize two reliable services guaranteeing timeliness properties in the presence of Byzantine failures, namely the clock synchronization and the /spl delta/-Atomic Broadcast. We identify necessary and sufficient conditions to ensure the correctness of both services in the scattered byzantine failure model.