How can I enforce an Internet access control policy?

If you wish to ensure that web browsing during company time is strictly for
business use, you would have to install a product that can enforce this
policy. There are two ways of doing this:

1. Installing a proxy server with content control feature
2. Installing a network monitor/scanner with content control feature.

If you use number 1, you will need to reconfigure all your users browsers.
Additionally, you could suffer a performance penalty. If you already use a
proxy server such as Microsoft Proxy server, you do not need to reconfigure
though, and you can purchase add on modules that do content checking.

Option number 2 requires no network reconfiguration and can block all types
of internet traffic.

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