HPING

Ideal tool to verify the security policy of your firewall

Creates entirely scaped ip packets, allows you to change protocol, TOS, fragmentation, MTU, ...

Superb tool for "dumb host scanning"

Host A = attacker, B = silent host that does not generate much traffic, C = victim
Ping host B, wait to see if ID increases with equal number each time
Spoof packets coming from host B, destination host C
Now, remembering the 3-way handshake:
- host B supposedly sent SYN to host C, host C replies with RST or SYN/ACK; in case it replies with SYN/ACK, host B will reply to it with RST => ID increases with more than normal