The real question is protecting from who and what. Tere is no such thing as secured online. If it states it is secure, it's only a matter of days until someone cracks it. Data protection online is commonly measured with common sense. Changing the file extension already protects your data only it's my manual way of rearranging and protecting things.
Change file extension when not in use and changing it back to original state when you need it and that's just the basics.
