diff --git a/Security/README.md b/Security/README.md
index eab48b72bd..02f2650fe5 100644
--- a/Security/README.md
+++ b/Security/README.md
@@ -173,17 +173,11 @@ For more information on each mitigation please visit https://aka.ms/exchangevuln
 
 For this script to work you must have the IIS URL Rewrite Module installed which can be done via this script using the -FullPathToMSI parameter.
 
-For IIS 10 and higher URL Rewrite Module 2.1 must be installed, you can download version 2.1 here:
+URL Rewrite Module 2.1 must be installed, you can download version 2.1 here:
 
 * x86 & x64 -https://www.iis.net/downloads/microsoft/url-rewrite
 
-For IIS 8.5 and lower Rewrite Module 2.0 must be installed, you can download version 2.0 here:
-
-* x86 - https://www.microsoft.com/en-us/download/details.aspx?id=5747
-
-* x64 - https://www.microsoft.com/en-us/download/details.aspx?id=7435
-
-Installing URL Rewrite version 2.1 on IIS versions 8.5 and lower may cause IIS and Exchange to become unstable. If there is a mismatch between the URL Rewrite module and IIS version, ExchangeMitigations.ps1 will not apply the mitigation for CVE-2021-26855. You must uninstall the URL Rewrite module and reinstall the correct version.
+For systems running IIS 8.5 and lower KB2999226 must be installed. Please review the pre-reqs for this KB and download from https://support.microsoft.com/en-us/topic/update-for-universal-c-runtime-in-windows-c0514201-7fe6-95a3-b0a5-287930f3560c"
 
 Script requires PowerShell 3.0 and later and must be executed from an elevated PowerShell Session.
 
@@ -218,4 +212,4 @@ For usage information, please read the top of the file.
 
 Download the latest release here:
 
-[Download http-vuln-cve2021-26855.nse](https://github.com/microsoft/CSS-Exchange/releases/latest/download/http-vuln-cve2021-26855.nse)
+[Download http-vuln-cve2021-26855.nse](https://github.com/microsoft/CSS-Exchange/releases/latest/download/http-vuln-cve2021-26855.nse)
\ No newline at end of file
diff --git a/Security/src/ExchangeMitigations.ps1 b/Security/src/ExchangeMitigations.ps1
index a5d5c0ae7b..df07f2b667 100644
--- a/Security/src/ExchangeMitigations.ps1
+++ b/Security/src/ExchangeMitigations.ps1
@@ -122,84 +122,105 @@ param(
     [switch]$AutoDownloadURLRewrite
 )
 
-function GetMsiProductVersion {
-    param (
-        [string]$filename
+function BackendCookieMitigation {
+    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseApprovedVerbs', '', Justification = 'Invalid rule result')]
+    param(
+        [string]$WebSiteName = "Default Web Site",
+        [switch]$RollbackMitigation
     )
 
-    try {
-        $windowsInstaller = New-Object -com WindowsInstaller.Installer
-
-        $database = $windowsInstaller.GetType().InvokeMember(
-            "OpenDatabase", "InvokeMethod", $Null,
-            $windowsInstaller, @($filename, 0)
-        )
-
-        $q = "SELECT Value FROM Property WHERE Property = 'ProductVersion'"
-
-        $View = $database.GetType().InvokeMember(
-            "OpenView", "InvokeMethod", $Null, $database, ($q)
+    function Get-MsiProductVersion {
+        param (
+            [string]$filename
         )
 
         try {
-            $View.GetType().InvokeMember("Execute", "InvokeMethod", $Null, $View, $Null) | Out-Null
+            $windowsInstaller = New-Object -com WindowsInstaller.Installer
 
-            $record = $View.GetType().InvokeMember(
-                "Fetch", "InvokeMethod", $Null, $View, $Null
+            $database = $windowsInstaller.GetType().InvokeMember(
+                "OpenDatabase", "InvokeMethod", $Null,
+                $windowsInstaller, @($filename, 0)
             )
 
-            $productVersion = $record.GetType().InvokeMember(
-                "StringData", "GetProperty", $Null, $record, 1
+            $q = "SELECT Value FROM Property WHERE Property = 'ProductVersion'"
+
+            $View = $database.GetType().InvokeMember(
+                "OpenView", "InvokeMethod", $Null, $database, ($q)
             )
 
-            return $productVersion
-        } finally {
-            if ($View) {
-                $View.GetType().InvokeMember("Close", "InvokeMethod", $Null, $View, $Null) | Out-Null
+            try {
+                $View.GetType().InvokeMember("Execute", "InvokeMethod", $Null, $View, $Null) | Out-Null
+
+                $record = $View.GetType().InvokeMember(
+                    "Fetch", "InvokeMethod", $Null, $View, $Null
+                )
+
+                $productVersion = $record.GetType().InvokeMember(
+                    "StringData", "GetProperty", $Null, $record, 1
+                )
+
+                return $productVersion
+            } finally {
+                if ($View) {
+                    $View.GetType().InvokeMember("Close", "InvokeMethod", $Null, $View, $Null) | Out-Null
+                }
             }
+        } catch {
+            throw "Failed to get MSI file version the error was: {0}." -f $_
         }
-    } catch {
-        throw "Failed to get MSI file version the error was: {0}." -f $_
     }
-}
-function Get-InstalledSoftwareVersion {
-    param (
-        [ValidateNotNullOrEmpty()]
-        [string[]]$Name
-    )
 
-    try {
-        $UninstallKeys = @(
-            "HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall",
-            "HKLM:\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall"
+    function Get-InstalledSoftwareVersion {
+        param (
+            [ValidateNotNullOrEmpty()]
+            [string[]]$Name
         )
 
-        New-PSDrive -Name HKU -PSProvider Registry -Root Registry::HKEY_USERS | Out-Null
+        try {
+            $UninstallKeys = @(
+                "HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall",
+                "HKLM:\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall"
+            )
 
-        $UninstallKeys += Get-ChildItem HKU: | Where-Object { $_.Name -match 'S-\d-\d+-(\d+-){1,14}\d+$' } | ForEach-Object {
-            "HKU:\$($_.PSChildName)\Software\Microsoft\Windows\CurrentVersion\Uninstall"
-        }
+            New-PSDrive -Name HKU -PSProvider Registry -Root Registry::HKEY_USERS | Out-Null
 
-        foreach ($UninstallKey in $UninstallKeys) {
-            $SwKeys = Get-ChildItem -Path $UninstallKey -ErrorAction SilentlyContinue
-            foreach ($n in $Name) {
-                $SwKeys = $SwKeys | Where-Object { $_.GetValue('DisplayName') -like "$n" }
+            $UninstallKeys += Get-ChildItem HKU: | Where-Object { $_.Name -match 'S-\d-\d+-(\d+-){1,14}\d+$' } | ForEach-Object {
+                "HKU:\$($_.PSChildName)\Software\Microsoft\Windows\CurrentVersion\Uninstall"
             }
-            if ($SwKeys) {
-                foreach ($SwKey in $SwKeys) {
-                    if ($SwKey.GetValueNames().Contains("DisplayVersion")) {
-                        return $SwKey.GetValue("DisplayVersion")
+
+            foreach ($UninstallKey in $UninstallKeys) {
+                $SwKeys = Get-ChildItem -Path $UninstallKey -ErrorAction SilentlyContinue
+                foreach ($n in $Name) {
+                    $SwKeys = $SwKeys | Where-Object { $_.GetValue('DisplayName') -like "$n" }
+                }
+                if ($SwKeys) {
+                    foreach ($SwKey in $SwKeys) {
+                        if ($SwKey.GetValueNames().Contains("DisplayVersion")) {
+                            return $SwKey.GetValue("DisplayVersion")
+                        }
                     }
                 }
             }
+        } catch {
+            Write-Error -Message "Error: $($_.Exception.Message) - Line Number: $($_.InvocationInfo.ScriptLineNumber)"
         }
-    } catch {
-        Write-Error -Message "Error: $($_.Exception.Message) - Line Number: $($_.InvocationInfo.ScriptLineNumber)"
     }
-}
-function GetURLRewriteLink {
-    $DownloadLinks = @{
-        "v2.1" = @{
+
+    function Test-IIS10 {
+        $iisRegPath = "hklm:\SOFTWARE\Microsoft\InetStp"
+
+        if (Test-Path $iisRegPath) {
+            $properties = Get-ItemProperty $iisRegPath
+            if ($properties.MajorVersion -eq 10) {
+                return $true
+            }
+        }
+
+        return $false
+    }
+
+    function Get-URLRewriteLink {
+        $DownloadLinks = @{
             "x86" = @{
                 "de-DE" = "https://download.microsoft.com/download/D/8/1/D81E5DD6-1ABB-46B0-9B4B-21894E18B77F/rewrite_x86_de-DE.msi"
                 "en-US" = "https://download.microsoft.com/download/D/8/1/D81E5DD6-1ABB-46B0-9B4B-21894E18B77F/rewrite_x86_en-US.msi"
@@ -212,7 +233,6 @@ function GetURLRewriteLink {
                 "zh-CN" = "https://download.microsoft.com/download/D/8/1/D81E5DD6-1ABB-46B0-9B4B-21894E18B77F/rewrite_x86_zh-CN.msi"
                 "zh-TW" = "https://download.microsoft.com/download/D/8/1/D81E5DD6-1ABB-46B0-9B4B-21894E18B77F/rewrite_x86_zh-TW.msi"
             }
-
             "x64" = @{
                 "de-DE" = "https://download.microsoft.com/download/1/2/8/128E2E22-C1B9-44A4-BE2A-5859ED1D4592/rewrite_amd64_de-DE.msi"
                 "en-US" = "https://download.microsoft.com/download/1/2/8/128E2E22-C1B9-44A4-BE2A-5859ED1D4592/rewrite_amd64_en-US.msi"
@@ -226,64 +246,87 @@ function GetURLRewriteLink {
                 "zh-TW" = "https://download.microsoft.com/download/1/2/8/128E2E22-C1B9-44A4-BE2A-5859ED1D4592/rewrite_amd64_zh-TW.msi"
             }
         }
-        "v2.0" = @{
-            "x86" = @{
-                "de-DE" = "https://download.microsoft.com/download/0/5/0/05045383-D280-4DC6-AE8C-81764118B0F9/rewrite_x86_de-DE.msi"
-                "en-US" = "https://download.microsoft.com/download/6/9/C/69C1195A-123E-4BE8-8EDF-371CDCA4EC6C/rewrite_2.0_rtw_x86.msi"
-                "es-ES" = "https://download.microsoft.com/download/1/D/9/1D9464B8-9F3B-4A86-97F2-AEC2AB48F481/rewrite_x86_es-ES.msi"
-                "fr-FR" = "https://download.microsoft.com/download/1/2/9/129A2686-9654-4B2A-82ED-FC7BCE2BCE93/rewrite_x86_fr-FR.msi"
-                "it-IT" = "https://download.microsoft.com/download/2/4/A/24AE553F-CA8F-43B3-ACF8-DAC526FC84F2/rewrite_x86_it-IT.msi"
-                "ja-JP" = "https://download.microsoft.com/download/A/6/9/A69D23A5-7CE3-4F80-B5AE-CF6478A5DE19/rewrite_x86_ja-JP.msi"
-                "ko-KR" = "https://download.microsoft.com/download/2/6/F/26FCA84A-48BC-4AEE-BD6A-B28ED595832E/rewrite_x86_ko-KR.msi"
-                "ru-RU" = "https://download.microsoft.com/download/B/1/F/B1FDE19F-B4F9-4EBF-9E50-5C9CDF0302D2/rewrite_x86_ru-RU.msi"
-                "zh-CN" = "https://download.microsoft.com/download/4/9/C/49CD28DB-4AA6-4A51-9437-AA001221F606/rewrite_x86_zh-CN.msi"
-                "zh-TW" = "https://download.microsoft.com/download/1/9/4/1947187A-8D73-4C3E-B62C-DC6C7E1B353C/rewrite_x86_zh-TW.msi"
-            }
-            "x64" = @{
-                "de-DE" = "https://download.microsoft.com/download/3/1/C/31CE0BF6-31D7-415D-A70A-46A430DE731F/rewrite_x64_de-DE.msi"
-                "en-US" = "https://download.microsoft.com/download/6/7/D/67D80164-7DD0-48AF-86E3-DE7A182D6815/rewrite_2.0_rtw_x64.msi"
-                "es-ES" = "https://download.microsoft.com/download/9/5/5/955337F6-5A11-417E-A95A-E45EE8C7E7AC/rewrite_x64_es-ES.msi"
-                "fr-FR" = "https://download.microsoft.com/download/3/D/3/3D359CD6-147B-42E9-BD5B-407D3A1F0B97/rewrite_x64_fr-FR.msi"
-                "it-IT" = "https://download.microsoft.com/download/6/8/B/68B8EFA8-9404-45A3-A51B-53D940D5E742/rewrite_x64_it-IT.msi"
-                "ja-JP" = "https://download.microsoft.com/download/3/7/5/375C965C-9D98-438A-8F11-7F417D071DC9/rewrite_x64_ja-JP.msi"
-                "ko-KR" = "https://download.microsoft.com/download/2/A/7/2A746C73-467A-4BC6-B5CF-C4E88BB40406/rewrite_x64_ko-KR.msi"
-                "ru-RU" = "https://download.microsoft.com/download/7/4/E/74E569F7-44B9-4D3F-BCA7-87C5FE36BD62/rewrite_x64_ru-RU.msi"
-                "zh-CN" = "https://download.microsoft.com/download/4/E/7/4E7ECE9A-DF55-4F90-A354-B497072BDE0A/rewrite_x64_zh-CN.msi"
-                "zh-TW" = "https://download.microsoft.com/download/8/2/C/82CE350D-2068-4DAC-99D5-AEB2241DB545/rewrite_x64_zh-TW.msi"
-            }
+
+        if ([Environment]::Is64BitOperatingSystem) {
+            $Architecture = "x64"
+        } else {
+            $Architecture = "x86"
         }
-    }
 
-    $IISVersion = Get-ItemProperty HKLM:\SOFTWARE\Microsoft\InetStp\ | Select-Object versionstring
+        if ((Get-Culture).Name -in @("de-DE", "en-US", "es-ES", "fr-FR", "it-IT", "ja-JP", "ko-KR", "ru-RU", "zn-CN", "zn-TW")) {
+            $Language = (Get-Culture).Name
+        } else {
+            $Language = "en-US"
+        }
 
-    if ($IISVersion.VersionString -like "* 10.*") {
-        $Version = "v2.1"
-    } else {
-        $Version = "v2.0"
+        return $DownloadLinks[$Architecture][$Language]
     }
 
-    if ([Environment]::Is64BitOperatingSystem) {
-        $Architecture = "x64"
-    } else {
-        $Architecture = "x86"
-    }
+    function Confirm-Signature {
+        param(
+            [string]$Filepath,
+            [string]$Stage
+        )
+        $MicrosoftSigningRoot2010 = 'CN=Microsoft Root Certificate Authority 2010, O=Microsoft Corporation, L=Redmond, S=Washington, C=US'
+        $MicrosoftSigningRoot2011 = 'CN=Microsoft Root Certificate Authority 2011, O=Microsoft Corporation, L=Redmond, S=Washington, C=US'
 
-    if ((Get-Culture).Name -in @("de-DE", "en-US", "es-ES", "fr-FR", "it-IT", "ja-JP", "ko-KR", "ru-RU", "zn-CN", "zn-TW")) {
-        $Language = (Get-Culture).Name
-    } else {
-        $Language = "en-US"
-    }
+        $IsValid = $false
+        $failMsg = "Signature of $Filepath not as expected. "
+        try {
+            if (!(Test-Path $Filepath)) {
+                $IsValid = $false
+                $failMsg += "Filepath does not exist"
+                throw
+            }
 
-    return $DownloadLinks[$Version][$Architecture][$Language]
-}
-Function BackendCookieMitigation {
-    [CmdLetBinding()]
-    param(
-        [System.IO.FileInfo]$FullPathToMSI,
-        [ValidateNotNullOrEmpty()]
-        [string[]]$WebSiteNames,
-        [switch]$RollbackMitigation
-    )
+            $sig = Get-AuthenticodeSignature -FilePath $Filepath
+
+            if ($sig.Status -ne 'Valid') {
+                $IsValid = $false
+                $failMsg += "Signature is not trusted by machine as Valid, status: $($sig.Status)"
+                throw
+            }
+
+            $chain = New-Object -TypeName System.Security.Cryptography.X509Certificates.X509Chain
+            $chain.ChainPolicy.VerificationFlags = "IgnoreNotTimeValid"
+
+            $chainsCorrectly = $chain.Build($sig.SignerCertificate)
+
+            if (!$chainsCorrectly) {
+                $IsValid = $false
+                $failMsg += "Signer certificate doesn't chain correctly"
+                throw
+            }
+
+            if ($chain.ChainElements.Count -le 1) {
+                $IsValid = $false
+                $failMsg += "Certificate Chain shorter than expected"
+                throw
+            }
+
+            $rootCert = $chain.ChainElements[$chain.ChainElements.Count - 1]
+
+            if ($rootCert.Certificate.Subject -ne $rootCert.Certificate.Issuer) {
+                $IsValid = $false
+                $failMsg += "Top-level certifcate in chain is not a root certificate"
+                throw
+            }
+
+            if ($rootCert.Certificate.Subject -eq $MicrosoftSigningRoot2010 -or $rootCert.Certificate.Subject -eq $MicrosoftSigningRoot2011) {
+                $IsValid = $true
+                Write-Verbose "[INFO] $Filepath is signed by Microsoft as expected, trusted by machine as Valid, signed by: $($sig.SignerCertificate.Subject), Issued by: $($sig.SignerCertificate.Issuer), with Root certificate: $($rootCert.Certificate.Subject)" -Verbose
+            } else {
+                $IsValid = $false
+                $failMsg += "Unexpected root cert. Expected $MicrosoftSigningRoot2010 or $MicrosoftSigningRoot2011, but found $($rootCert.Certificate.Subject)"
+                throw $failMsg
+            }
+        } catch {
+            $IsValid = $false
+            throw $failMsg
+        }
+
+        return $IsValid
+    }
 
     #Configure Rewrite Rule consts
     $HttpCookieInput = '{HTTP_COOKIE}'
@@ -296,41 +339,48 @@ Function BackendCookieMitigation {
     $filter = "{0}/rule[@name='{1}']" -f $root, $name
     $filter2 = "{0}/rule[@name='{1}']" -f $root, $name2
 
-    if (!$RollbackMitigation) {
-        Write-Verbose "[INFO] Starting mitigation process on $env:computername" -Verbose
-
-        #Check if IIS URL Rewrite Module 2 is installed
-        Write-Verbose "[INFO] Checking for IIS URL Rewrite Module 2 on $env:computername" -Verbose
+    Import-Module WebAdministration
 
-        #If IIS 10 check for URL rewrite 2.1 else URL rewrite 2.0
-        $RewriteModule = Get-InstalledSoftwareVersion -Name "*IIS*", "*URL*", "*2*"
-        $IISVersion = Get-ItemProperty HKLM:\SOFTWARE\Microsoft\InetStp\ | Select-Object versionstring
-
-        $RewriteModuleInstallLog = ($PSScriptRoot + '\' + 'RewriteModuleInstallLog.log')
-
-        #Install module
-        if ($RewriteModule) {
+    if ($RollbackMitigation) {
+        Write-Verbose "[INFO] Starting mitigation rollback process on $env:computername"
+        $site = "IIS:\Sites\$WebSiteName"
 
-            #Throwing an exception if incorrect rewrite module version is installed
-            if ($IISVersion.VersionString -like "*10.*" -and ($RewriteModule.Version -eq "7.2.2")) {
-                throw "Incorrect IIS URL Rewrite Module 2.0 Installed. You need to install IIS URL Rewrite Module 2.1 to avoid instability issues."
+        $mitigationFound = $false
+        foreach ($f in @($filter, $filter2)) {
+            if (Get-WebConfiguration -Filter $f -PSPath $site) {
+                $mitigationFound = $true
+                Clear-WebConfiguration -Filter $f -PSPath $site
             }
-            if ($IISVersion.VersionString -notlike "*10.*" -and ($RewriteModule.Version -eq "7.2.1993")) {
-                throw "Incorrect IIS URL Rewrite Module 2.1 Installed. You need to install IIS URL Rewrite Module 2.0 to avoid instability issues."
+        }
+
+        if ($mitigationFound) {
+            $Rules = Get-WebConfiguration -Filter 'system.webServer/rewrite/rules/rule' -Recurse
+            if ($null -eq $Rules) {
+                Clear-WebConfiguration -PSPath $site -Filter 'system.webServer/rewrite/rules'
             }
 
-            Write-Verbose "[INFO] IIS URL Rewrite Module 2 already installed on $env:computername" -Verbose
+            Write-Verbose "[OK] Rewrite rule mitigation removed for $env:COMPUTERNAME :: $website"
+        } else {
+            Write-Verbose "[INFO] Rewrite rule mitigation does not exist for $env:COMPUTERNAME :: $website"
+        }
+    } else {
+        Write-Verbose "[INFO] Starting mitigation process on $env:computername" -Verbose
+        Write-Verbose "[INFO] Checking for IIS URL Rewrite Module on $env:computername" -Verbose
+        $RewriteModule = Get-InstalledSoftwareVersion -Name "*IIS*", "*URL*", "*2*"
+
+        if ($RewriteModule) {
+            Write-Verbose "[INFO] IIS URL Rewrite Module already installed on $env:computername" -Verbose
         } else {
 
-            #IfAutoDownloadURLRewrite
             if ($AutoDownloadURLRewrite) {
                 Write-Verbose -Message "ExchangeMitigations.ps1 will now attempt to download and install the IIS URL Rewrite Module on $env:computername" -Verbose
                 try {
                     # Force TLS1.2 to make sure we can download from HTTPS
                     [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
                     $ProgressPreference = "SilentlyContinue"
+                    $DownloadLink = Get-URLRewriteLink
                     $DownloadDir = Join-Path $env:TEMP "IISUrlRewrite"
-                    $DownloadLink = GetURLRewriteLink
+                    $RewriteModuleInstallLog = Join-Path $DownloadDir "\RewriteModuleInstall.log"
                     $FullPathToMSI = Join-Path $DownloadDir "\$($DownloadLink.Split("/")[-1])"
                     if (!(Test-Path $DownloadDir)) {
                         New-Item -ItemType Directory $DownloadDir | Out-Null
@@ -339,92 +389,77 @@ Function BackendCookieMitigation {
                     $response = Invoke-WebRequest $DownloadLink -UseBasicParsing
                     [IO.File]::WriteAllBytes($FullPathToMSI, $response.Content)
                 } catch {
-                    throw $_
+                    throw "[ERROR] $_"
                 }
-            }
-
-            if ($FullPathToMSI) {
-
-                $MSIProductVersion = GetMsiProductVersion -filename $FullPathToMSI
-
-                #If IIS 10 assert URL rewrite 2.1 else URL rewrite 2.0
-                if ($IISVersion.VersionString -like "*10.*" -and $MSIProductVersion -eq "7.2.2") {
-                    throw "Incorrect MSI for IIS $($IISVersion.VersionString), please use URL rewrite 2.1"
-                }
-                if ($IISVersion.VersionString -notlike "*10.*" -and $MSIProductVersion -eq "7.2.1993") {
-                    throw "Incorrect MSI for IIS $($IISVersion.VersionString), please use URL rewrite 2.0"
-                }
-
-                Write-Verbose "[INFO] Installing IIS URL Rewrite Module 2" -Verbose
-                $arguments = " /i " + '"' + $FullPathToMSI.FullName + '"' + " /quiet /log " + '"' + $RewriteModuleInstallLog + '"'
-                $msiexecPath = $env:WINDIR + "\System32\msiexec.exe"
-                Start-Process -FilePath $msiexecPath -ArgumentList $arguments -Wait
-                Start-Sleep -Seconds 15
-                $RewriteModule = Get-InstalledSoftware -Name *IIS* | Where-Object { $_.Name -like "*URL*" -and $_.Name -like "*2*" }
-                if ($RewriteModule) {
-                    Write-Verbose "[OK] IIS URL Rewrite Module 2 installed on $env:computername"
-                } else {
-                    throw "[ERROR] Issue installing IIS URL Rewrite Module 2, please review $($RewriteModuleInstallLog)"
+            } elseif ($FullPathToMSI -and (Test-Path $FullPathToMSI)) {
+                try {
+                    $MSIPath = (Resolve-Path $FullPathToMSI).Path
+                    $RewriteModuleInstallLog = Join-Path (Get-Item $MSIPath).DirectoryName -ChildPath "RewriteModuleInstall.log"
+                } catch {
+                    throw "[ERROR $_"
                 }
-            } else {
-                throw "[ERROR] Unable to proceed on $env:computername, path to IIS URL Rewrite Module MSI not provided and module is not installed."
             }
-        }
 
-        foreach ($website in $WebSiteNames) {
-            Write-Verbose "[INFO] Applying rewrite rule configuration to $env:COMPUTERNAME :: $website"
+            $MSIProductVersion = Get-MsiProductVersion -filename $FullPathToMSI
 
-            $site = "IIS:\Sites\$($website)"
+            if ($MSIProductVersion -lt "7.2.1993") {
+                throw "[ERROR] Incorrect IIS URL Rewrite Module downloaded on $env:computername"
+            }
 
-            try {
-                if ((Get-WebConfiguration -Filter $filter -PSPath $site).name -eq $name) {
-                    Clear-WebConfiguration -Filter $filter -PSPath $site
-                }
+            #KB2999226 required for IIS Rewrite 2.1 on IIS ver under 10
+            if (!(Test-IIS10) -and !(Get-HotFix -Id "KB2999226" -ErrorAction SilentlyContinue)) {
+                throw "[ERROR] Did not detect the KB2999226 on $env:computername. Please review the pre-reqs for this KB and download from https://support.microsoft.com/en-us/topic/update-for-universal-c-runtime-in-windows-c0514201-7fe6-95a3-b0a5-287930f3560c"
+            }
 
-                if ((Get-WebConfiguration -Filter $filter2 -PSPath $site).name -eq $name2) {
-                    Clear-WebConfiguration -Filter $filter2 -PSPath $site
-                }
+            Write-Verbose "Installing the IIS URL Rewrite Module on $env:computername" -Verbose
 
+            $arguments = "/i `"$FullPathToMSI`" /quiet /log `"$RewriteModuleInstallLog`""
+            $msiexecPath = $env:WINDIR + "\System32\msiexec.exe"
 
-                Add-WebConfigurationProperty -PSPath $site -filter $root -name '.' -value @{name = $name; patternSyntax = 'Regular Expressions'; stopProcessing = 'False' }
-                Set-WebConfigurationProperty -PSPath $site -filter "$filter/match" -name 'url' -value $inbound
-                Set-WebConfigurationProperty -PSPath $site -filter "$filter/conditions" -name '.' -value @{input = $HttpCookieInput; matchType = '0'; pattern = $pattern; ignoreCase = 'True'; negate = 'False' }
-                Set-WebConfigurationProperty -PSPath $site -filter "$filter/action" -name 'type' -value 'AbortRequest'
+            if (!(Confirm-Signature -filepath $FullPathToMSI -Stage $stage)) {
+                throw "[ERROR] File present at $FullPathToMSI does not seem to be signed as expected, stopping execution."
+            }
 
-                Add-WebConfigurationProperty -PSPath $site -filter $root -name '.' -value @{name = $name2; patternSyntax = 'Regular Expressions'; stopProcessing = 'True' }
-                Set-WebConfigurationProperty -PSPath $site -filter "$filter2/match" -name 'url' -value $inbound
-                Set-WebConfigurationProperty -PSPath $site -filter "$filter2/conditions" -name '.' -value @{input = $HttpCookieInput; matchType = '0'; pattern = $pattern2; ignoreCase = 'True'; negate = 'False' }
-                Set-WebConfigurationProperty -PSPath $site -filter "$filter2/action" -name 'type' -value 'AbortRequest'
+            Start-Process -FilePath $msiexecPath -ArgumentList $arguments -Wait
+            Start-Sleep -Seconds 15
+            $RewriteModule = Get-InstalledSoftwareVersion -Name "*IIS*", "*URL*", "*2*"
 
-                Write-Verbose "[OK] Rewrite rule configuration complete for $env:COMPUTERNAME :: $website"
-                Get-WebConfiguration -Filter $filter -PSPath $site
-                Get-WebConfiguration -Filter $filter2 -PSPath $site
-            } catch {
-                throw $_
+            if ($RewriteModule) {
+                Write-Verbose "[OK] IIS URL Rewrite Module installed on $env:computername"
+            } else {
+                throw "[ERROR] Issue installing IIS URL Rewrite Module, please review $($RewriteModuleInstallLog)"
             }
         }
-    } else {
-        Write-Verbose "[INFO] Starting mitigation rollback process on $env:computername"
-        foreach ($website in $WebSiteNames) {
 
-            $site = "IIS:\Sites\$($website)"
+        Write-Verbose "[INFO] Applying URL Rewrite configuration to $env:COMPUTERNAME :: $WebSiteName" -Verbose
+        $site = "IIS:\Sites\$WebSiteName"
 
-            $MitigationConfig = Get-WebConfiguration -Filter $filter -PSPath $site
-            if ($MitigationConfig) {
+        try {
+            if ((Get-WebConfiguration -Filter $filter -PSPath $site).name -eq $name) {
                 Clear-WebConfiguration -Filter $filter -PSPath $site
-                Clear-WebConfiguration -Filter $filter2 -PSPath $site
+            }
 
-                $Rules = Get-WebConfiguration -Filter 'system.webServer/rewrite/rules/rule' -Recurse
-                if ($null -eq $Rules) {
-                    Clear-WebConfiguration -PSPath $site -Filter 'system.webServer/rewrite/rules'
-                }
-                Write-Verbose "[OK] Rewrite rule mitigation removed for $env:COMPUTERNAME :: $website"
-            } else {
-                Write-Verbose "[INFO] Rewrite rule mitigation does not exist for $env:COMPUTERNAME :: $website"
+            if ((Get-WebConfiguration -Filter $filter2 -PSPath $site).name -eq $name2) {
+                Clear-WebConfiguration -Filter $filter2 -PSPath $site
             }
+
+            Add-WebConfigurationProperty -PSPath $site -filter $root -name '.' -value @{name = $name; patternSyntax = 'Regular Expressions'; stopProcessing = 'False' }
+            Set-WebConfigurationProperty -PSPath $site -filter "$filter/match" -name 'url' -value $inbound
+            Set-WebConfigurationProperty -PSPath $site -filter "$filter/conditions" -name '.' -value @{input = $HttpCookieInput; matchType = '0'; pattern = $pattern; ignoreCase = 'True'; negate = 'False' }
+            Set-WebConfigurationProperty -PSPath $site -filter "$filter/action" -name 'type' -value 'AbortRequest'
+
+            Add-WebConfigurationProperty -PSPath $site -filter $root -name '.' -value @{name = $name2; patternSyntax = 'Regular Expressions'; stopProcessing = 'True' }
+            Set-WebConfigurationProperty -PSPath $site -filter "$filter2/match" -name 'url' -value $inbound
+            Set-WebConfigurationProperty -PSPath $site -filter "$filter2/conditions" -name '.' -value @{input = $HttpCookieInput; matchType = '0'; pattern = $pattern2; ignoreCase = 'True'; negate = 'False' }
+            Set-WebConfigurationProperty -PSPath $site -filter "$filter2/action" -name 'type' -value 'AbortRequest'
+
+            Write-Verbose "[OK] Rewrite rule configuration complete for $env:COMPUTERNAME :: $website"
+        } catch {
+            throw "[ERROR] Mitigation failed on $env:COMPUTERNAME :: $WebSiteName - $_"
         }
     }
 }
+
 Function UnifiedMessagingMitigation {
     [CmdLetBinding()]
     param(
@@ -474,6 +509,7 @@ Function UnifiedMessagingMitigation {
         Get-Service MSExchangeUMCR
     }
 }
+
 Function ECPAppPoolMitigation {
     [CmdLetBinding()]
     param(