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I am trying to configure endpoint machines with a firewall that only allows white-listed traffic, and all other connections are blocked.

The client machines are desktops and laptops running Windows 7 (both x86 and x64) using the built-in Windows Firewall with Advanced Security. Every machine is part of a Windows Server 2008 domain, and I am configuring the firewall using Group Policy. I am testing this firewall configuration with a small subset of machines.

Right now, I have Windows Firewall configured to block all inbound and outbound traffic that doesn't match an explicit allow rule. Here are the basic communications that are currently enabled:

  • DNS (UDP 53 Out)
  • LDAP (TCP 389 Out, UDP 389 Out)
  • Remote Desktop (TCP 3389 Out)
  • Web Browsing (TCP 80 Out)
  • Preset: Core Networking
  • Preset: Distributed Transaction Coordinator
  • Preset: File and Printer Sharing
  • Preset: Network Discovery
  • Preset: Remote Assistance

In addition, I have a few rules defined for the business applications we use. This has been working fairly well, but today I encountered some problems with MSRPC (Microsoft Remote Procedure Call).

I open mmc.exe and load the computer management snap-in in order to modify the local administrators group. In the "Select Users, Computers..." window I enter the username, then click "Check Names". It gives me the following error:

Windows cannot process the object with the name "Foo Bar" because of the following error:

Access is denied.

When I remove the firewall restrictions, it works fine. The traffic being blocked is MSRPC, and it uses a randomly selected port in the range of [49100...65535].

How can I create a rule for Windows Firewall that allows MSRPC traffic without creating an overly broad rule, such as allowing TCP traffic on all ports?

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2 Answers 2

KB154596 "How to configure RPC dynamic port allocation to work with firewalls"

In short, it looks like you're going to be deploying a lot of registry changes via a GPO. Make sure to document all that you do and why you've done it. If anyone else has to curate the systems there, it will be quite a shock to see something as basic as RPC hardwired to certain ports. Not that it's bad, mind you. Just different.

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up vote 0 down vote accepted

I created a Windows Firewall rule that allows all TCP traffic for %SystemRoot%\System32\mmc.exe and that completely solved the problem.

In addition, I noticed two other programs that also need to have all TCP traffic allowed:

  • %SystemRoot%\System32\spoolsv.exe
  • %ProgramFiles%\Hyper-V\vmconnect.exe
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