The Microsoft Internet Information Services Team has released the beta for the Dynamic IP Restrictions Extension for IIS 7. The tool provides IT Professionals and Hosters a configurable module that helps block Denial of Service attacks or cracking of passwords.
It supports IIS 7/7.5 on Windows Server 2008, Windows Vista SP1, Windows Server 2008 R2 or Windows 7.

It determines which IP addresses to temporarily block by detecting a pattern that could be conducive to such attacks. This module can be configured such that the analysis and blocking could be done at the Web Server or the Web Site level. Blocking of IP addresses is based on number of concurrent requests or on number of requests over a period of time. The requests can be logged, and you can determine the response that can be returned by IIS (403, 404 or drop the connection)
IIS Manager can display the current list of blocked IP addresses. IPV4 and IPV6 are both fully supported.

The Dynamic IP Restrictions for IIS 7.0 tool provides the same functionality that exists in IIS 7.0 built-in IPv4 and Domain Restrictions. Because of that the Dynamic IP Restrictions is provided as a replacement for IPv4 and Domain Restrictions.

To download to tool and get further information, visit the Microsoft IIS Website