How to avoid unauthorized access of webservices?

Hi Friends

I have been using webservices developed in c# in my current project that is deployed on client’s intranet. In the phase II client wants to use this application on the internet i.e. wants to connect other offices located different part of country. Earlier since it was an intranet application we didn’t secure webservices i.e. anyone can access it from intranet using its address. Now I want to secure the webservices, in other words these services should only be accessible from the authorized application.

Waiting for reply

Thanks
Diya

http://www.codeproject.com/Articles/5085/WS-Security-Web-services-the-secure-way

I usually take five minutes to hit Google up before bothering to post a question, but hey.... that's just me.

That's one example, there's others.