Add an IP address to a black-list for an IIS website.

Add-IpToIisBlacklist.ps1

function Add-IpToIisBlacklist($websiteName, $ip, $subnetMask = $null) {
    Add-Type -Path "$env:SystemRoot\System32\inetsrv\Microsoft.Web.Administration.dll"
    $manager = New-Object Microsoft.Web.Administration.ServerManager
    $config = $manager.GetApplicationHostConfiguration();
    $cpSecConfig = $config.GetSection("system.webServer/security/ipSecurity", $websiteName)

    $cpSecCollection = $cpSecConfig.GetCollection()
    $newAdd = $cpSecCollection.CreateElement("add")
    $newAdd["ipAddress"] = $ip
    if ($subnetMask) {
        $newAdd["subnetMask"] = $subnetMask
    }
    $newAdd["allowed"] = $false
    $cpSecCollection.Add($newAdd) | Out-Null
    $manager.CommitChanges();
    $manager.Dispose()
}