A Firewall has the task to examine data traffic across borders between networks, and to reject those packets, which do not have a permission for transmission. Beside attempts to access directly a computer in the protected network, there are also attacks against the Firewall itself, or attempts to outwit a Firewall with falsified data packets.
Such break-in attempts are recognized, repelled and logged by the Intrusion Detection system (IDS). Thereby it can be selected between logging within the device, email notification, SNMP traps or SYSLOG alarms. IDS checks the data traffic for certain properties and detects in this way also new attacks proceeding with conspicuous patterns.