The firewall is your network or computer’s first line of defense against external attacks which are meant to gain access to critical information. In order to be truly effective, system administrators and computer owners can implement various types of firewall techniques to fortify their defenses against malicious attacks. Common types of firewall techniques are:
1.Packet Filter- inspects every packet that enters or leaves your network applying rules defined by the user
2.Circuit-Level Gateway – security mechanism applied to UDP or TCP connections
3.Application Gateway – application specific security mechanism like Telnet and FTP servers
4.Proxy Server – hides the real network address by intercepting incoming and outgoing messages that flow through the network