IPtables Mod:
1) Keep all existing setup on "whitelist only" instead of "everything open"
2) Create a new web page that runs only on port 81
3) Be sure the web page is NOT "index" so it must be addressed directly (no guessing, make it an impossible to guess page name like "akjsajg816j1283ja.php"). Consider rotating it regularly and sending the dynamic agents a link every morning before work if you're really security conscious.
4) That new web page has one purpose: Check user/pass against vicidial_users table (borrow the code from any vicidial page!) and if the user authenticates, add their IP address to the iptables "good" file managed by the "Recent" module in iptables.
This module allows the creation of a file that can be checked against within the iptables system.
5) If an entry is present or absent, special action can be taken. In this case, the action would be ACCEPT, thus after logging in to this page the agent is now "whitelisted" until reboot when that file is cleaned out.
We charge $100 to install this in a standard Vicibox installation, as we've already invested the time to create it.

And you're right, it was fun to make. I'd like to make it part of Vicibox. Maybe I'll suggest that to Kumba

So: Perhaps this could be an "option" at installation?
We also have a version that's merely a table in mysql written to the same "good" file at reboot and each time the table is altered. Allows a manager to add a good ip without putty/ssh. We've considered modifying this to acquire IP addresses from the phone table (so the manager could manually place the ip in the phone record and iptables would just suddenly allow that ip past the firewall for access). Simple change to our existing system.
If this were to be part of 4.0, I would be quite proud.
