Howtoforge posted a guide about preventing MySQL injection attacks with GreenSQL on Debian Etch

GreenSQL (or greensql-fw) is a firewall for MySQL databases that filters SQL injection attacks. It works as a reverse proxy, i.e., it takes the SQL queries, checks them, passes them on to the MySQL database and delivers back the result from the MySQL database. It comes with a web interface (called greensql-console) so that you can manage GreenSQL through a web browser. This guide shows how you can install GreenSQL and its web interface on a Debian Etch server.

Preventing MySQL Injection Attacks With GreenSQL On Debian Etch