UPDATE: as if to underscore the importance of this tool and approach, yesterday a story hit about a SQL Injection attack infecting over 132,000 systems in short order. Net-Security have the full details on this attack, including how it probes the host via JavaScript to check for known vulnerabilities, how it exploits them, and how it ultimately downloads a back-door trojan to get the game going. It’s really amazing to see how complicated and professional these things have gotten, and just adds to the reasoning that we have to step up to the plate and learn how to better defend against them.
I’ve been privy to some log dumps showing real, and successful, SQL attacks on some MSSQL servers before, and they weren’t pretty. Of course a SQL injection attack has little to do with the database (well, as long as it’s still SQL based at least (nod to CouchDB and MongoDB)), and more with the code that calls it, and how that code deals with sanitizing inputs. For this reason MySQL is just as vulnerable, after all, bad code is bad code. While a client of mine opted for a firewall ‘module’ they had to buy an additional licence for, that set them back many thousands of dollars (annually!) I knew there had to be cheaper/better ways to address this kind of vulnerability. One way of course is to fix the code, but with legacy sites that no one has touched for years, this may be impractcal (I didn’t say this, I only heard it as reasoning from management), and the other idea is to proxy the SQL and ‘clean’ it before it hits the database. The advantage of this approach is that it protects against known attacks, as well as unknown attacks, since it limits so much of what an attack is allowed to accomplish when trying to get its’ foot in the door. This approach is what the folks over at GreenSQL have done, and it’s very impressive. They sum things up nice and sweet with, “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 & PostgreSQL . 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.”
UPDATE: I recently used this 
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