Captive Portal

Hello -

At the library I work at, we are using a m0n0wall-powered captive portal (v1.235) and it is working great. Today I got an email from my ISP telling me that the outside IP address that our captive portal uses has spambots sending email out of it, and that if we don't fix it they will take action. I am guessing that a person has a laptop that has been compromised in to a spam zombie.

When I tried to put rules on the LAN interface to block IMAP/POP3/SMTP and block all DNS requests to anywhere except the m0n0wall box, the rules all worked as they are supposed to, but the captive portal stopped running. People are able to surf, but the login window (in our case just an acceptable use policy) does not appear and they are not redirected to our home page. It's not enough even to disable the rules I put in, I had to delete them entirely.

What am I doing wrong?

I think you need to enable DNS on the local lan for the redirection to occur. Some one please correct me if I'm wrong. Blocking SMTP outbound is all you need.

@drbeep  - you are right, DNS must be enabled for the captive portal to work. One of the first things the captive portal does is to allow dns query once successful and users tries to connect to the website, splash page kicks in. One can't access a page before DNS determins its domain IP.