A firewall is a system that prevents unauthorized to your computer use and access. The firewall can be software, hardware, or a combination of both. They are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the Intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. It is important to remember that a firewall does not remove the computer virus problems, but that when used in conjunction with regular updates of the operating system and a good anti-virus software, will add some security and protection additional to your computer or network. Hardware the hardware firewall firewall provide a strong protection from most forms of attack that come from the outside world and can be purchased as a stand-alone product or broadband routers.
Unfortunately, fighting against viruses, worms and Trojans, a hardware firewall can be less effective than a software firewall, because it could not detect worms in emails. Software for home users, the most widely used firewall firewall is a software firewall. A good software firewall will protect your computer against attempts to control or access your computer from the outside, and usually provides additional protection against Trojans and E-mail worms most common. The disadvantage of software firewalls is that they protect only the computer on which are installed and do not protect a network. There are several types of techniques Firewall Packet filter: looks at each packet that enters or leaves the network and accepts or rejects based on user-defined rules.
The packet filtering is fairly effective and transparent to users, but is difficult to configure. In addition, it is susceptible to IP spoofing. Application gateway: applies security mechanisms to certain applications, such as ftp and telnet servers. This is very effective, but it can produce a decrease in benefits. Circuit-level gateway: applies mechanisms of security when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further testing. Proxy server: intercepts all messages entering and leaving the network. Proxy server effectively hides the true network addresses. In practice, many firewalls use two or more of these techniques at the same time. A firewall is the first line of defense in protecting private information. For greater security, data can be encrypted. Original author and source of the article.