How can I determine what is transmitting data? Recently I noticed that even while no applications are actively running (at home screen), the up and down arrows under the WiFi status bar item are turning on/off.  This is a recent change, and seems to have started after some automatic updates. 

I've gone through and killed all the running processes (that allow you to kill them), and the behavior continues.  I'm assuming it must be a system process that's causing this, but I can't for the life of me figure out which one or why.

I have a Samsung Galaxy S4 with KitKat 4.4.2, if that matters. And I've already tried restarting the device.

How can I determine what is causing the WiFi indicator to signal data is being transferred? I'm comfortable creating simple android applications, so a programming solution is an option.
I use an application called “App Snitch” which monitors all network access and let’s you know what each app is doing. The Play Store link is HERE.