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YogenderKumar
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A firewall is a security barrier that prevents unauthorized access to or from private networks. Businesses use this combination of hardware, software and corporate policies to prevent Internet users outside the business from accessing proprietary data on the business's networks that are connected to the Internet, as well as private intranets. Firewalls are also used to control employee access to Internet resources. The most common business firewall technique uses a firewall server in conjunction with a proxy server to screen packets of data. All data entering or leaving an organization passes through the firewall. The firewall examines each packet and determines whether to forward it to its destination, based on security policies set up by the firewall administrator or IT department. The proxy server replaces the network IP address with another, contingent address. This process effectively hides the network IP address from the rest of the Internet, thereby protecting the network. Firewalls can be inconvenient for business users who are protected by them. For example, users may be unable to access an external e-mail provider or to upload files to external servers. Some standardized Internet plug-ins, such as RealPlayer, cannot function through firewalls. Some of the new video plug-ins used on news Web sites are also unable to operate through firewalls. If your employer's firewall interferes with work you need to conduct on the Internet, you should work with your IT department's firewall administrators to achieve a level of protection that allows you to access necessary resources.