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Firewall & its Techniques !!

April 23, 2012

firewall is a device or set of devices designed to permit or deny network transmissions based on a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass.

Many personal computer operating systems include software-based firewalls to protect against threats from the public Internet. Many routers that pass data between networks contain firewall components and, conversely, many firewalls can perform basic routing functions .

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                                                             Fig : Firewall

Firewall Techniques :

There are several types of firewall techniques:

  • 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.
  • In practice, many firewalls use two or more of these techniques in concert. A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.

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