Enabling Microsoft File and Print Sharing with Norton Internet Security / Norton Personal Firewall

Situation:

You have a home network connected to the Internet, and after installing Norton Internet Security or Norton Personal Firewall, you cannot connect to other machines on your home network.

Solution:

Due to serious security issues with many installations of File and Print Sharing, Norton Internet Security products block access by default.  You will need to configure Norton Internet Security to permit certain network services in order to connect to other machines on your home network.  File and Print Sharing uses the NetBIOS software interface, and can be used over IPX, NetBEUI, or the default TCP/UDP transport.  There 

There are three services used by Microsoft File and Print Sharing (using the NetBIOS software interface).  These are:

netbios-ns (nbname): NetBIOS name service.  This is used for identifying machines on the network.  On UDP, it uses port 137.

netbios-dgm (nbdatagram): NetBIOS datagram service.  The datagram service operates over UDP port 138 for data transfer.

netbios-ssn (nbsession): NetBIOS session service.  This is used for file and print sharing connections.  It uses TCP port 139.

When trying to connect to another machine to use file and print sharing on it, you must enable the inbound "netbios-ns" connection.  To do this, follow these steps:

    1. Open Norton Internet Security or Norton Personal Firewall.
    2. Click Options and select Internet Security.
    3. Click Advanced Options.
    4. Click the Firewall tab.
    5. Scroll through the rules list and look for the following rule:

Default Inbound NetBIOS Name

6. Select "Default Inbound NetBIOS Name" and click Modify.

7. Change Action from Block to Permit.

8. Click OK.

Once you have done this, you will be able to connect to other computers on a local area network.  It will also allow your NetBIOS name information out on the internet as well.

Allowing the NetBIOS name to go out over the internet is not a major security risk, but can allow others on the internet to know what you called your computer, what your network cardÆs address is, and what file shares you may have. After this process, this information will be available on the internet, but FILE SHARING WILL STILL BE PROTECTED. The actual file and print sharing ability requires the NetBIOS Session, which is handled in a separate rule (called Default Block NetBIOS Networking).

More Information:

For more information on NetBIOS and file and print sharing, see the NetBIOS FAQ. 

For more detailed information on more secure models of home networking, and how to share files on a machine protected with Norton Internet Security, see the knowledge base articles on interaction between computers on a LAN and setting up a small network. 

Additional details on setting up a trusted relationship between computers on a local network can be found in the user's manual (Troubleshooting / Questions about Home Networking section).