Firewall

Firewall: A software that is made to protect your computer from unknown crackers that trying to get on your computer.

Any of a number of security schemes that prevent unauthorized users from gaining access to a computer network or that monitor transfers of information to and from the network. Source: [|www.dictionary.com]

There are several types of firewall techniques: Source: [] Firewall is ment to secure and protect your computer from harmfull viruses and unautherized users.
 * Packet filter:** Looks at each [|packet] entering or leaving the [|network] and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to [|IP spoofing].
 * Application gateway:** Applies security mechanisms to specific applications, such as [|FTP] and [|Telnet] [|servers]. This is very effective, but can impose a performance degradation.
 * Circuit-level gateway:** Applies security mechanisms when a [|TCP] or [|UDP] connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
 * Proxy server:** Intercepts all messages entering and leaving the network. The [|proxy server] effectively hides the true network addresses.