GreenSQL is an Open Source database firewall used to protect databases from SQL injection attacks. GreenSQL works as a proxy for SQL commands and has built in support for MySQL. The logic is based on evaluation of SQL commands using a risk scoring matrix as well as blocking known db administrative commands (DROP, CREATE, etc). GreenSQL is distributed under the GPL license.

GreenSQL Architecture

GreenSQL works as a reverse proxy for MySQL connections. It means, that instead of MySQL server, your applications will connect to GreenSQL server. GreenSQL will analyze SQL queries and forward them to the back-end MySQL server.

The following picture describes the whole process.

As you can see, GreenSQL calls real database server to execute SQL commands and web application connects to GreenSQL server as if it is a real database server.

GreenSQL can be installed together with database server on the same computer or it can use a distinct server. By default GreenSQL listens on local port 127.0.0.1:3305 redirecting SQL requests to 127.0.0.1:3306 (default MySQL settings). This settings could be altered using GreenSQL Console.

Source : GreenSQL