Optical Fiber cable is one of the Best possible solutions for spikes as it is less probe to electrical interference . While lightning please dont take chances if you connected your Broadband through telephone or connected your computer directly to the electricity. Even if you put one of best ELCB in place, there is a greater chance that it will fail when you needed the most...
Tom
As far as the transaction ATM is concerned, it is an ATOMIC transaction and normally ATM machines are connected to UPS. Regarding net connectivity , I think it s through broadband or ISDN line which can cause connectivity problems through Lightning..
I would like to add one more point , even if you install Lightning arresters in your house, there is again a chance that, the same may not work when needed the most..
Tom