Example 1 ICMP Bombing. Most firewalls and routers can screen ICMP traffic. However ICMP is used for legitimate purposes such as Ping and screening ICMP messages in routers can cause network problems. Firewalls that are a single point of connectivity correctly interpret ICMP without letting it through. Firewalls can block and log all source routed packets and tools like TCP wrappers can detect source routed packets and trigger alarms.
Many routers can block source routed packets.
Magic These are attacks that nobody has thought of yet. Such attacks if and when discovered will be full of surprises. Combination attacks Attackers are likely to use a combination of the above methods when seeking to gain unauthorised access or to deny service etc. This phase of the attack can be categorised as Social Engineering. The user downloads the program and runs it causing all his messages to be deleted, and exposing the password file to the attacker.