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The most popular implementation of a web proxy is a proxy cache server. This server receives an HTTP request from a web browser and then makes the request on behalf of the sending workstation. When the requested page

is returned, the proxy server caches a copy of the page locally. The next time someone requests the same web page or Internet information, the page can be delivered from the local cache instead of the proxy server having to formulate a new request to the web server on the Internet. This speeds up web surfing for commonly accessed pages. Web proxies can also increase network security by filtering out content that is considered insecure, such as executables, scripts, or viruses.

FTP Proxy

FTP proxies handle the uploading and downloading of files from a server on behalf of a workstation. An FTP proxy operates in a fashion similar to that of a web proxy. As with web proxies, FTP proxies can filter out undesirable content (viruses and the like).

SMTP Proxy

SMTP proxies handle Internet e-mail. Here, the actual contents of the packet and mail can be automatically searched. Any packets or messages that contain material that is not considered secure can be blocked. Many SMTP proxies allow network virus protection software to scan inbound mail.

Not every firewall falls into a category. Traditional firewall vendors are adding features to their firewalls to make them difficult to classify. Vendors who traditionally offered packet-filtering solutions are now also offering proxy solutions, and vendors who traditionally offered proxy solutions are now also offering packet-filtering solutions. The network administrator can now get a packet-filtering firewall and a proxy firewall combined into one product. Dual-style firewalls are considered hybrids.

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