Firewall

- Firewall is a system designed to prevent unauthorized access to private network.

- Prevents unauthorized users accessing private networks connected to internet, especially Intranet.

- All messages entering or leaving the intranet pass through the firewall.

- Firewall examines each message and blocks which dosn't meet the security criteria.

Techniques of Firewall

Packet Filtering

Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules.

Application Gateway

Applies security mechanisms to specific applications, such as FTP and Telnet servers.

Circuit-level Gateway

Applies security mechanisms when a TCP connection is established.

Proxy Server

Proxy server effectively hides the true network addresses by intercepting all messages entering and leaving the network.