Firewall is a technical hurdle intended to avoid unofficial or unnecessary communications among computer networks or hosts.
A firewall is considered to shelter your computer from assault by malevolent users or by spiteful software such as bugs that use spontaneous received network traffic to hit your computer. Before you stop your firewall, you must detach your computer from every part of networks, as well as the Internet. You can put into practice firewalls in software, hardware, or some time both. Firewalls are commonly used to avoid unconstitutional Internet users from accessing personal networks that are attached to the Internet.
There are several firewall techniques and each firewall may use two or more than two techniques in concert.
Packet filters: - This firewall technique is observed the entering and discharging the network of each packet. Packets filters admit or discard it depend on user-defined rules. Packet filtering is quite efficient and transparent to users, but it is hard to build up. Packets filter used to liable to IP spoofing.
Application gateway: - Application gateway used to apply safety method to definite applications, such as Telnet and FTP servers. Application gateways are very effective, but can inflict presentation poverty.
Circuit-level gateway: - Circuit-level gateway is concerned to security device especially when UDP or TCP connection is going to establish. When connection comes visible then packets can run among the hosts without additional checking.
Proxy server:-Proxy server interrupts all messages incoming and outgoing the network. The proxy server successfully hides the true network addresses.