Password protect web service

Is it possible to require user name and password for a web service without changing t开发者_StackOverflowhe code for existing web service?

Adding a DLL and configuration would be OK, but I rather not change the web service.

Use (Windows - Integrated Windows) in IIS this is the only way to apply authentication without changing a single bit of code. Here is the article also contains other options as well.

http://msdn.microsoft.com/en-us/library/w67h0dw7.aspx

Simplest way is to let IIS protect the folder where the web service resides. No code change required.