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Consider systemwide software instead of localized files for better security
I have found that software like 'DNS Kong' or 'PeerBlocker' are extremely simple to manage and they will effectively isolate the entire system from unwanted IP ranges. This type of software (there are others available for all common operating systems in use) is faster and easier to manage than fiddling about with localized text files. For the most security though, take the time to effectively program your hardware switch and set up the ranges there where the chance of hacking is far less likely.