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Windows Firewall blocks file sharing

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Have you ever come across a situation where you want to access another computer via its Firewall OptionsUNC (\\computer-name\share) and came across a "Network Path not found" error? Although not too uncommon, this errors can puzzle you in cases where you know all the services required for file sharing are running. I faced this issue the other day and finally after a bit of tussle, I managed to solve the problem. We were trying to access a computer at one of our remote locations and it was giving this error. What made this even more puzzling was that local users were able to access the same computer by using the UNC path. We tried all we could and knew but still the error was the same.

Then I searched on the internet and found some references and a very useful knowledge base article (KB article number 840634) on Microsoft support website which addressed this issue. Apparently somebody had enabled the firewall and the firewall is designed to block File and Printer Sharing from any network and allow access only in the same subnet in its default configuration.

To allow file and print sharing on your computers from any network, follow the steps described below:

  1. Click on Start --> Settings --> Control Panel. If you are using the Windows XP Start Menu, you can find the Control Panel on the right side of the start menu.
  2. Category view: In the category view, click on the Security center and then click on Windows Firewall to open the Windows Firewall configuration window. In the Classic view, you will see the Windows Firewall icon.
  3. Ensure that the Do not Allow Exceptions check box is not checked on the General tabEnable Ports
  4. Click on Exceptions tab and highlight File and Printer Sharing and click on modify the settings. The file and printer sharing is done through port number 445.
  5. Highlight the TCP 445 and click on Change scope... or just double click to edit it. In the resulting screen, select whether you want to enable for any network for just your network or for a custom list of networks. In case you choose custom list of networks, you will have to manually enter each subnet you want to enable for it to work.
  6. Click OK your way out and now you should be able to access the computer(s) over the network using UNC path.

A word of caution: I don't recommend setting the scope to Any as is shown here. It means that anyone who can reach your network will be able to access the computer over the network. Either select just the subnet you are on or explicitly define the subnets that you know and trust that would be required to connect remotely using UNC path.

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Re:Windows Firewall blocks file sharing

Posted by Anonymous User at Apr 23, 2007 12:19 PM

I use DynDNS. Many moons ago I found a registry hack that enabled me to access my home Windows XP fileshares using UNC and DynDNS (eg. \\\MyShare). I have since re-installed Windows XP and now cannot access my shares using UNC and DynDNS over the Internet, and I can no longer find the registry entry to enable this (note: UNC will work over the Internet if I use the ISP assigned IP address, so I can ping, get the IP address, and then do: \\\MyShare).

Does anyone out there know what it is? It's driving me crazy.

Many thanks.

Re:Windows Firewall blocks file sharing

Posted by William E. Triest III at Sep 22, 2008 06:23 AM

My best guess of the problem would be the firewall is blocking you. By default file and printer sharing only opens up to the local network, you have to manually go in and open it up to the internet.

Open up the firewall settings (Start->Control Panel->Windows Firewall) and go to the Exceptions Tab. Select File and Printer Sharing and click the edit button. I'm not positive all the ports are necessary, but select a port and hit the change scope button. Change the Scope from My Network (subnet) only to Any Computer (including those on the Internet). Hit Ok. Then select a different port and repeat the process.

It is your computer, so ultimately it is your decision, but I would highly recommend against this. Google for the port numbers for explanations as to why this is a bad idea.

Re:Windows Firewall blocks file sharing

Posted by Paul Barrett at Apr 26, 2010 10:16 AM

Windows Server 2003 - Thanks for this for some reason when I tackled this before it didn't dawn on me that each protocol had its own scope. Once I change the scope for all of the protocols for my specific subnets. And checked the scopes on other services and protocols everything worked beautifully.

Thanks for pointing out to click on 445.

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