Thank you for the post.
By default, a new FileMaker database will have a Full Access account of Admin with no password. The file will "Log in Using" the Admin account until secured with a password. File > File Options will show if an account is set to automatically log in (see the screenshot below).
Since security in FileMaker is a rather broad topic, the following articles may be of assistance:
Thank you so much. This is exactly what I was looking for. I have only a few days experience in this and I'm loving every minute I'm using this database. Big learning curve but it's fun :)