Some Security attack in network system how protect them.......

Finding a way into the network to attack: Attacker find a way to attack in network system.
--------For this reason use Firewall. it can be hardware or software.

Attacker find out software bugs, buffer overflows to attack the system.
------- That's why use Intrusion Detection Systems.

Denial of Service or DoS: A Attacker make unusable of a system by overloading server.
-------For protect use Ingress filtering, IDS

TPSec: This is a protocol to protect network layer
--------Its use for TCP hijaking