If you want to keep your network free of certain applications, such as Skype, your policy must clearly state that they are prohibited. It must also present the penalties for any employee found using them.
It's always helpful to state why certain rules and restrictions are in place. Use of a particular application, for example, could slow down the network for essential tasks and communications. I'd back this up with graphs or statistics showing the effect certain apps have on the availability of bandwidth. People are far less likely to circumvent or ignore policy rules if they understand the logic behind them.
Just having a policy, however, is not enough. To make policy enforcement the norm within an organization, you must be able to detect and punish violators, and this requires technology. There's an abundance of products to choose from that control users' network activities. I personally like Web security gateways, such as the Web Security Gateway from Websense Inc. Deploying this type of technology, along with sensible rules, will manage your data and control employees so that your organization can benefit from social networking tools while avoiding many of the dangers. A tool like Microsoft's Windows SteadyState can also help system administrators control what users can and can't do, such as access programs, configuration settings, removable storage devices and websites.
A security policy is essential to manage how enterprise resources, like bandwidth, are used as it's the document that binds all of your security controls together, making sure they complement and strengthen each other. Failure to enforce your policy and apply the stated penalties, however, will render it moot. This is why you need to back it up with technology to not only monitor any misuse, but also to preempt any attempted misuse, either intentional or through simple oversight.
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This was first published in August 2009