Simple question - is SSL necessary to secure credentials?

I have what I'm sure is a basic question:

If I don't access FileVista over HTTPS, does the FileVista login screen pass credentials as plain text?

I plan to run it over the internet, but want to be sure it is secure.  I'm not really worried about the file xfers being encrypted as much as I am about the login credentials being secured.

Before I run out and install an SSL cert I wanted to be sure this is even necessary to address my concerns.

Thanks, and sorry for the noob question.