But I presume the best security would be to walk down the road and use the ATM or bank branch.
You would be appalled to know how many embedded systems (like the software on ATMs and medical devices) still run on Windows XP - which hasn't had a security update in almost 2 years. There's a lot of custom software out there (like the service center management used by car dealers) that will not run on Vista, Win7 or Win10 (forget about 8).
