I just want to give a general piece of advice. If you are going to deal with sensitive data of others (for instance, credit card numbers) in a hostile environment (the internet), you better be well prepared, and really know your stuff.

The kind of questions you are asking sets off all kinds of alarms bells for me; it just screams "I don't really know what I'm doing, and what to defend against" between the lines.

Prepare yourself well. Go follow a course. Follow another one. Pick the brains of experienced people - people you trust. Make a plan. Shred it. Make a better plan. Present that plan to co-workers. Have them shred it. Make an even better plan. Don't just post a bunch of lose questions on perlmonks.

Abigail