This paper presents a computational analysis of the noise associated with the ion current in single open ion channels. The study is performed by means of a coupled molecular dynamics/Monte Carlo approach able to simulate the conduction process on the basis of all microscopic information today available from protein structural data and atomistic simulations. The case of potassium ions permeating the KcsA channel is considered in the numerical calculations. The results show a noise spectrum different from what is theoretically predicted for Poisson noise, confirmed by the existence of a correlation in ion-exit events.