CS4 General ideas on how to implement a secure area in flash site

Hi,
This is what needs to happen.
user comes to the client section of the site.
Types his/her password into the input text box.
Clicks the button related to his/her company.
Is sent to a section of the site only accessible in this way. Multiple secure sections for different companies.
Here they can view confidential information.
AND download confidential documents.

What is the best way to do secure login within a flash site?

How do I make sure the server folder with the documents is secure even from outside flash?

I am hoping to have all the documents be password protected PDF's as well for an extra layer of security.

I have never had to deal with security before.
General concepts as well as real methods code hints all required!!!

Thanks mark

I've created a base login system in AS3(and AS2) with php/mysql that my be able to get you started in the right direction

Normal style login/signup: http://flashden.net/item/as3-php-mys...675?ref=rondog

User must activate account: http://flashden.net/item/as3-php-mys...674?ref=rondog

Admin must activate account: http://flashden.net/item/as3-php-mys...673?ref=rondog

Hi,
admin must activate seems to be just what I am looking for.
Two questions, say I have several sections for the companies clients. (it is a TV commercial production company)
If a client were to leave one company with a login area and go work for the opposition who were also a client with a login area, can the admin delete that user from the original login. Don't want them stealing their previous employers ideas!

Second question, how can I do mutliple secure areas?

your solution looks awesome by the way
thanks
mark