This article applies to PRTG Network Monitor 13 or later

Monitoring Sessions per Specific Sites

As an alternative to the approaches described below, you can also try using this script to get the results of the IIS sessions:

$computer = $args

$namespace = "root\CIMV2"
$userSessions = Get-wmiObject -class Win32_PerfRawData_W3SVC_WebService -computername $computer -namespace $namespace | select-object -expand currentanonymoususers

$users=$usersessions[0]

Write-Host "<prtg>"
"<result>" 
"<channel>Total Users connected to IIS</channel>" 
    
"<value>"+ $users +"</value>" 
"</result>"

"<text>Total of " + $users + " users connected</text>"
Write-Host "</prtg>"

The line $users=$usersessions[0] can be edited to use other instances of your IIS server. If you use the WMI tester, run the query

SELECT name,currentanonymoususers FROM Win32_PerfRawData_W3SVC_WebService

You will see all of the IIS instances along with their current user value and can then change your array selection in the code accordingly.

For example if the WMI tester comes back with

Then you could change the line $users=$usersessions[0] to $users=$usersessions[1] for Default Site or $users=$usersessions[2] for the OpenMan site.