The cheapest would be to "hurry-it-up." If you go online, do your business, and get off, the chances of anyone violating your privacy is extremely unlikely. It is not like someone is hanging around campgrounds waiting to capture someone else's data. Those kind of people are generally pretty darn lazy and are looking for a much more productive use of their time -- read "not much work." Besides, Banks have their own security systems in place that would far surpass anything you could afford. (If Paranoia still has a grip on you, then you should set up your own "hotspot" with something like an Aircard and a Router. The folks at, for instance, http://3gstore.com/ could lead you through that process.)