Microsoft KB Archive/913735

= Applications that require DCOM cannot connect to network resources after Windows Live OneCare is installed =

Article ID: 913735

Article Last Modified on 5/23/2006

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APPLIES TO


 * Windows Live OneCare

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SYMPTOMS
When you run an application that requires DCOM on a computer that has Microsoft Windows Live OneCare installed, you may receive an error message. The error message states that the application cannot connect to network resources.

Note The error message varies depending on the application you are running.



CAUSE
This problem may occur when Windows OneCare Firewall is enabled. By default, Windows OneCare Firewall blocks port 135. This port is required by DCOM.



RESOLUTION
Important These steps may increase your security risk. These steps may also make your computer or your network more vulnerable to attack by malicious users or by malicious software such as viruses. We recommend the process that this article describes to enable programs to operate as they are designed to, or to implement specific program capabilities. Before you make these changes, we recommend that you evaluate the risks that are associated with implementing this process in your particular environment. If you choose to implement this process, take any appropriate additional steps to help protect your system. We recommend that you use this process only if you really require this process.

To resolve this issue, follow these steps to open port 135:
 * 1) In the Windows OneCare display, click View or change settings.
 * 2) Click the Firewall tab.
 * 3) Under Other settings, click Advanced Settings.
 * 4) Click the Ports and Protocols tab.
 * 5) Click Add.
 * 6) In the Name box, type DCOM.
 * 7) Under Protocol, click TCP or UDP.
 * 8) In the TCP or UDP list, click TCP.
 * 9) In both Port Range boxes, type 135.
 * 10) In the Direction box, click Inbound under Settings.
 * 11) Under Scope, click Internet.
 * 12) Click OK two times.



MORE INFORMATION
Applications that require DCOM must query the Svchost.exe process to open port 135 for listening. However, when Windows Live OneCare Firewall is enabled, the Svchost.exe process does not have permission to open port 135. Windows Live OneCare Firewall blocks DCOM because some viruses can take advantage of vulnerabilities in DCOM. For the same reason, Windows Live OneCare Firewall does not let you add the Svchost.exe process to the exception list.

