See this link for more information.
Security is addressed here. Some useful links:
If your database is behind a firewall, it will not be directly accessible from the Cloud. There are two main options in this case:
1 - Open a port in your firewall
For most people, this is a difficult and unattractive option. Organizations are usually reluctant to create holes in their firewall (which, after, exist for a reason). Nevertheless, if this is an option for you, it can be a quick and efficient solution.
2 - Use reverse SSH tunneling
Don't let the name scare you: reverse SSH tunneling is very easy to set up, and remarkably effective.