You can use SSH over the Internet by opening a port in your router configuration just as it is demonstrated in the Synchronizing files over the Internet recipe. When doing so, your Banana Pi's SSH server is accessible over the Internet. This means that everybody is able to log in to your Banana Pi. This is especially risky if you have not changed the default password.
There are several methods to improve the security of your SSH server on the Internet. The three most used methods are: