On every Mac guest access of personal file sharing is on by default, and there is no easy way to turn it off.
Having file sharing on by default can be a security risk, because everyone in your network can copy files to the `Drop Box` or read files from your Public folder.
Sure, you can change the permissions or turn sharing off, but it`s more effective if you turn guest access off and, with Guest Access, you can turn it off very easy.
NOTE: Guest Access is licensed under a Creative Commons License.
