Events Per Second, or EPS, as it is commonly referred to in the world of network security, is a measurement that is used to convey how fast a network generates data from its security devices (firewalls, Intrusion Detection Systems (IDS), servers, routers, etc.), and/or how fast an SEM product can correlate data from those devices. A savvy buyer will match the EPS his network is generating to those that can be accommodated by the SEM tool that he is purchasing.