in reply to Encrypting Credit card numbers
This has a couple of implications:
The intermediary is an "application server", and is either housed on its own box (a "three tier" configuration), or it's colocated with the database. (Big players go three tier, with firewalls between each tier).
Writing a simple application server is actually pretty easy. Code for accepting socket connections is widely available, so that part shouldn't be too difficult. (Lincoln Stein's Network Programming with Perl is a great reference.) Accessing the database is also pretty easy.
The trickier part is in designing the protocol. A simple way to start is to look at your existing queries in terms of inputs and outputs, and to wrap each query up inside of a "command" that the web server will then send to the application server. If you use XML to express the inputs and outputs, you're on the road to XML-RPC or SOAP.
If you get this far, and assuming that your application protocol doesn't include something like getAllCreditCardNumbers(), then the credit card data as a whole is probably safe, though encrypting it in the database might help you sleep at night.