SQL injection attacks can allow hackers to execute arbitrary SQL commands on your database through your Web site. To avoid these attacks, every piece of data supplied by a user on a Web form, through HTTP Post or CGI parameters, or other means, must be validated to not contain information that is not expected. GreenSQL is a firewall for SQL -- it sits between your Web site and MySQL database and decides which SQL statements should and should not be executed. At least that's the idea -- in execution, I found some open doors.
The article continues at http://www.linux.com/feature/145341