Windows Tip Sheet
Unleash the WMI Within
Configure Windows Firewall to accept incoming traffic.
Over at ScriptingAnswers.com
(my Web site on administrative scripting), we’ve had a number
of users fighting with Windows XP SP2 issues related to Windows
Management Instrumentation (WMI) scripting. Turns out that SP2 locks
down computer security a bit tighter than some folks realized, leaving
you to pick up the pieces and reconfigure things so that your old
WMI-related scripts will still work.
Not Just Windows Firewall
Sure, Windows Firewall causes some problems by blocking the incoming
traffic trying to talk to the WMI service. In other words, a script
running on one machine won’t be able to connect to WMI on
a remote machine unless Windows Firewall is modified. Of course,
you should first make sure that your WMI script works against the
local machine—then you can start debugging SP2 security issues.
Remote WMI scripting needs to perform two basic tasks: First, it
needs to establish a connection to the remote WMI service. An XP
machine running the script will allow the outgoing traffic through
Windows Firewall, but the target machine’s Windows Firewall
will block the traffic. You need to configure the firewall so that
the Windows Firewall: Allow remote administration
exception is enabled; this will punch a hole for the incoming
WMI traffic. The other thing WMI needs is Distributed Component
Object Model (DCOM) permissions to run; Administrators on local
machines have the necessary DCOM permissions, but ordinary users
don’t. If you need them to, give them the DCOM Remote Launch
permission on the target machine(s), using the DCOM configuration
utility (Start, Run, DCOMCNFG).
Some WMI connections are made asynchronously, which means the computer
issuing the request can go about its business until a response comes
in from the remote machine. This traffic needs to make it through
the requesting computer’s firewall, which requires the firewall
to allow traffic on TCP port 135. Run netsh
firewall add portopening tcp 135 DCOM_port to do it.
There’s more detail in Knowledge Base (KB) article 875605
to cover different situations, such as anonymous connections. No
doubt, though, SP2’s beefy new security features have sacrificed
a level of functionality in favor of tighter security, so you’ll
need to carefully test everything in your environment to see what
reconfigurations are necessary.
| Remember that, by default, Windows
Firewall disables most incoming traffic except the
basics like file and print sharing. Everything else—Remote
Desktop, Windows Messenger and so forth—may
require you to add an exception. Windows Firewall
will normally offer to create the exception for
you the first time you run an application, by popping
up a dialog and asking if you’d like to keep
blocking (don’t create an exception) or stop
blocking (create an exception) the application.
Trying to configure your Windows Firewall settings
but find that the user interface is disabled (grayed
out)? There’s a Group Policy responsible,
being applied from Active Directory and centrally
configuring the Windows Firewall settings on your
machine. Windows disables the user interface as
a visual cue that any changes you make wouldn’t
have any effect, anyway.
- Microsoft has a KB
article on this very set of problems.
- Join the scripting discussion at ScriptingAnswers.com.
- Check out my
series of free Microsoft TechNet Webcasts on administrative
- Read more about troubleshooting Windows Firewall in SP2 here.
Don Jones is a multiple-year recipient of Microsoft’s MVP Award, and is an Author/Evangelist for video training company Pluralsight. Don is also a co-founder and President of PowerShell.org, a community dedicated to Microsoft’s Windows PowerShell technology. Don has more than two decades of experience in the IT industry, and specializes in the Microsoft business technology platform. He’s the author of more than 50 technology books, an accomplished IT journalist, and a sought-after speaker and instructor at conferences worldwide. Reach Don on Twitter at @concentratedDon, or on Facebook at Facebook.com/ConcentratedDon.