If you would like to block an IP address from accessing your website you can do so via the web.config file in your websites wwwroot.
Place the following code within the <system.webServer> tags in the web.config file:
<security>
<!-- line allows everyone, except below IP-->
<ipSecurity allowUnlisted="true">
<clear/>
<!-- blocks the specific IP -->
<add ipAddress="xx.xx.xx.xx"/>
</ipSecurity>
</security>replacing xx.xx.xx.xx with the valid IP address.
