A Firewall is a part of a computer system or network that is specifically designed to prevent and deny any unauthorized Internet users from accessing private networks connected to the Internet or accessing your computer without any lawful consent. It can be implemented in either hardware or software, and even combination of both.
Benefits of Firewall :
- Protect private local area networks (LANs) from hostile intrusion from the Internet
- Allow network administrators to offer access to specific types of Internet services to selected LAN users
- Filters protocols and services that are either not necessary or that cannot be adequately secured from exploitation
- Conceal names of internal systems or electronic mail addresses, thereby revealing less information to outside hosts
- Centralized and simplified network services management
Several types of firewall techniques:
Packet filter
Inspects every packet that passed through the network and choose to either accepts or rejects it based on user-defined rules. Although it is difficult to configure, but proven that it is fairly effective and mostly transparent to its users. It is susceptible to IP spoofing.
Application gateway
Applies security mechanisms to specific applications, such as FTP and Telnet servers. Although it might imposes a performance degradation but it is very effective in performing its task.
Circuit-level gateway
Applies security mechanisms when a TCP or UDP connection is established where once the connection has been made, packets can flow between the hosts without the need of further checking or inspection.
Proxy server
intercepts all messages that enter and leave the network and can effectively hides the user’s true network addresses.
