Question

In Windows Firewall Exceptions tab, I have the following entry ticked:

@xpsp3res.dll,-20000

I'm wondering if it is a harmful entry added by some Malware?

Resolution

By looking at the DLL's string table using a resource editor, you can see the corresponding text string for the above entry. The entry @xpsp3res.dll,-20000 is related to Microsoft's Network Diagnostics Tool, and the text string is Network Diagnostics for Windows XP.

To resolve the string ID correctly, simply reinstall the Network Diagnostics Tool. On the other hand, if you've uninstalled the Network Diagnostics Tool recently, then simply select the entry @xpsp3res.dll,-20000 in the Windows Firewall Exceptions tab, and delete the entry.