MS03-039: A Buffer Overrun in RPCSS May Allow Code Execution

This is the latest security update from Microsoft. It appears that no one has released a virus/worm to exploit this issue, but installing this fix will protect you in the future.

From the Tech Note...

Remote Procedure Call (RPC) is a protocol that is used by Windows. RPC provides an inter-process communication mechanism that allows a program that is running on one computer to seamlessly access services on another computer. The protocol itself is derived from the Open Software Foundation (OSF) RPC protocol, but with the addition of some Microsoft-specific extensions.