The task of the firewall is to check the traffic crossing the boundaries between networks and to reject or drop packets that have no permission for transmission. Along with direct attacks on computers in protected networks, attacks can also be directed to the firewall itself, or attempts can be made to outwit the firewall with fake data packets.
These attempts are detected, repelled and logged by an intrusion detection system (IDS). There is a choice of alerts including in-device logging, e-mail messaging, SNMP traps or SYSLOG alarms. The IDS checks the traffic for certain properties and can detect new attacks from conspicuous patterns.
