Protecting scheduled tasks

Hello!

I am fairly new to CF's task scheduler, but I've found it to be a great feature.  I'm using it to send a series of emails each day, but I was wondering what the best way to protect it is.  I noticed the area for a username and password, but where do I define that information for the file?

Right now the file resides in a directory on my site.  It's "hidden," but it's still on the Web.  If anyone happens to find it, obviously all they have to do is hit the file and the script will run.  Is there another place I can store these files so that they still run properly, but are not online?  Does the username/password protection apply to the page when it's online, too?

Thank you!