Password-protect a webservice

 I'm developing a web application with access to a SQL Server 2008 database. What's the best option for me to upload new content to the database? How do you upload your own content to a web database, guys?
As now, I have a webservice that uploads my content to the database. But obviously I do not want that the "bad guys" upload content... So I was thinking about protecting the webservice with a password. Is it a good idea? Do you have any articles on how to do this? Do you have better ideas?
 
Thanks,
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