Bob has been getting warnings that he's "overdrawn" on his MiFi data plan and wants to know if he's been struck by the Heartbleed virus. Leo says no. Heartbleed attacks servers, not mobile devices. More likely, Bob has an app that is active and downloading everything. Someone may have also commandeered the system and is using it.
Leo says that Bob's ISP, Verizon, could tell him as they analyze the traffic. Regardless, Leo advises changing his passwords and then changing the SSIDs. He should also try and figure out what program is doing it. It could be an off site backup, or streaming video.