My Browser is Sentient

Noticed some weird traffic coming into my router this morning:

The incoming traffic (blue line) was maxed out at my bandwidth cap, even though I wasn't downloading anything. After a few failed attempts at figuring out what was going on, I started closing browser tabs, resulting in the sustained dropoff near the end of the graph. I reopened the tabs (small bump closer to the end) but the incoming traffic did not spike.

Gmail and a few other pages were open, but nothing that would explain the traffic spike I saw. Maybe the ghost in the machine was watching Hulu.