The simplest way seems to configure the webserver so no request other than from "your system" can be made to said webservice.

Otherwise, use some kind of authentication. There are thousands of techniques to choose from, many of them available in ready made source code, randing from simple and easy to use for the user, to very secure, and more hassle (work) for the user.

What's the best pick for you, is impossible to determine from the post.

In reply to Re: A question about web service security by JavaFan
in thread A question about web service security by Anonymous Monk

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