What is w3wp.exe?

Question

I have a WCF service running under a service user on my local system. Every time I try to debug it is giving me a message Attach Security warning.<

Answer 1

An Internet Information Services (IIS) worker process is a windows process (w3wp.exe) which runs Web applications, and is responsible for handling requests sent to a Web Server for a specific application pool.

It is the worker process for IIS. Each application pool creates at least one instance of w3wp.exe and that is what actually processes requests in your application. It is not dangerous to attach to this, that is just a standard windows message.