In an attempt to make life easier Apple added the Captive Network Assistant App to OS X. I think this addition was made sometime around Lion. Captive Network Assistant is an App that can display a little the very simple web page you get when you connect to a wifi network that has Captive Portal. These are the pages you get when you first log onto your coffee shop WiFi. They usually ask you to agree to some terms and conditions before you can use the network. In the case of hotels, resorts, and cruise ships they will also tie to the site billing system so you can be charged if that’s appropriate. Lately I’ve started to get these sites on both my MiFi hotspot and most lately, my home WiFi. This article explains three major drawbacks to Apple’s approach here. The authors of these web pages will frequently embed logout information into the page when the captive portal mechanism is being used to track usage for billing. In this use case, the app is a hinderance because when it disappears, it takes the logout link with it. Also, Apple triggers the app by attempting to fetch a known page over the web when your WiFi first connects. If it doesn’t get what it expects, it knows it’s behind a Captive Portal. In my case, the Captive Portal App is displaying Apple’s static page which indicates that you aren’t behind a portal.
When I started seeing captive portal on my home network, I decided the turn the thing off. To turn captive portal off do this command:
sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.captive.control Active -boolean false
To restore the old behavior, do this, again in a terminal window:
sudo defaults delete /Library/Preferences/SystemConfiguration/com.apple.captive.control Active
Other people including the article linked above recommend renaming the App. I’m not in love with that solution, mostly because two months from now I don’t expect to remember that I did this in the first place. My solution isn’t much better. One could argue it’s worse because it requires terminal and sudo. It’s the one I went with though.