I have a Windows 2008R2 Server running IIS 7.5. It is getting bombarded with attempted hacks from similar IPs.

How would I block the IP range with something like 51.255.65.*?

Below is the UI presented to me when adding a Deny restriction

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You need to specify the range in proper subnet format. You may wish to take a look at our canonical question on IPv4 subnetting, if you're not exactly sure what that means.

For your example, you'd use in the "IP address range" field, and the subnet mask of in the "Mask or Prefix" field.

If you're going to be making a habit of this (and also just in general), you may wish to find a nice subnet calculator or subnet mask cheat sheet you like, and add them to your bookmarks.

  • Thank you! So to clarify to block 51.255.*.* I would use with a Mask or Prefix of – Paul Hale Feb 23 '16 at 13:37
  • @PaulHale Yes, that looks correct. – HopelessN00b Feb 23 '16 at 14:55

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