Question [Q] Public Wifi Security

I will let you know I am a novice to actually understanding how wifi works, but I was wondering if there was an app that would temporarily shut down incoming/outgoing communications (through wifi only preferably) when I am connect to a public wifi like at school or some cafe? With the exception to allow use of dolphin or any other browser surf the web for less private matters. Why? So apps like facebook, banking, email, ebay's personal information cannot be intercepted by a hacker on the same network.Thanks!

I guess the other answer I am looking for is: Do apps like facebook resend password data on use when you have remained logged in from the last session?

EDIT: I have seen some permissions apps, and settings within my rom. Was wondering if there was something that would block all apps at once like a profile setting.
Samsung Galaxy S4 T-MOBILE - C-Rom