Added a try catch to first WMI call in the 'ByComputerName' parameter set. If the call fails the entire loop for that system will be terminated.

Author: dotps1

Functions/Test-WannaCryVulnerability.ps1

@@ -11,7 +11,7 @@
 .ProjectUri
     https://github.com/dotps1/PSFunctions
 .ReleaseNotes
-    Adding FullName for type Microsoft.Management.Infrastructure.CimSession, else Windows 8.1/WMF 5.0 cannot find the type.
+    Added a try catch to first WMI call in the 'ByComputerName' parameter set.  If the call fails the entire loop for that system will be terminated.
 
 #>
 
@@ -87,7 +87,7 @@ param (
     [Parameter(
         ParameterSetName = "ByComputerName"
     )]
-    [PSCredential]
+    [System.Management.Automation.PSCredential]
     $Credential = [PSCredential]::Empty,
 
     [Parameter(
@@ -151,15 +151,15 @@ process {
                 }
 
                 try {
-                    $osCaption = Get-WmiObject -ComputerName $nameValue -Class Win32_OperatingSystem -Property Caption -Credential $Credential |
+                    $osCaption = Get-WmiObject -ComputerName $nameValue -Class Win32_OperatingSystem -Property Caption -Credential $Credential -ErrorAction Stop |
                         Select-Object -ExpandProperty Caption
                 } catch {
-                    Write-Error $_.ToString()
+                    Write-Error -Message "Failed to contact WMI on '$nameValue'." -RecommendedAction "Verify WS-MAN is not being blocked by the firewall."
                     continue
                 }
 
                 if ($osCaption -match "Windows 10|2016") {
-                    Write-Error -Message "$osCaption is not vulnerable to WannaCry."
+                    Write-Warning -Message "$osCaption is not vulnerable to WannaCry."
                     continue
                 }