Such a VM should be well-maintained with latest updates.
closed as off topic by sysadmin1138♦ Aug 9 '12 at 17:18
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Personally? The best one is one installed and configured yourself and archived. That way it's configured for your needs and your use on your network. I don't know of a specific turnkey solution that is "best", and anything you keep having to download as an update will still require you to reconfigure it each time for your own use.