It appears that there is no security on the Public folder and can be accessed by anyone knowing your IP address (internal or external)
This is more vunarable if you use a external static IP
once you have found out what the external IP is ie 165.222.121.46
you can then map a network drive ie drive P: \165.222.121.46\Public
So any one has full access to you files ie delete, rename, steal photo etc
SOLUTION
Currently the only solution I have is to turn off Pubic Access on Public Folder
OPTIONAL
you may need to rename first the following folder Shared Pictures, Shared Music & Shared Videos to
Shared Pictures1, Shared Music1 & Shared Videos1 (THIS IS DUE TO A POSSIBLE ACCESS DENIED ISSUES)
Now recreate the folders with original names and move the contents of the renames folder over.
This can be done by renaming the Public Folder to Public1 (you will now recieve an error message) may beed to hit refresh
The Public Access slider is now available to turn off
renaming the Public1 back to Public (you will now recieve an error message) may beed to hit refresh
Now set user access to the Public Folder
Public folder should now be secure as users will no need username and password to use