Rep. Roscoe Bartlett (Rep.-Md.) issued that warning recently. He's not your typical "the-sky-is-falling" Congressman he's a former research scientist and engineer and has previously has worked on projects for NASA and the military. Bartlett issued his warning at a House Science subcommittee hearing about how to roll out the Smart Grid.
At the hearing, he warned that a weapon that fired an electromagnetic pulse (EMP) could wipe out significant sections of the Smart Grid. According to a Science News account of the hearings: EMP is a powerful and potentially devastating form of electromagnetic fallout. It's usually associated with nuclear weapons, although it can be triggered by any major explosive bursts. Unlike radioactive fallout, this rain won't directly harm living things. It will just catastrophically fry all electronics and modern electrical systems by inducing staggeringly large and rapid current or voltage surges.
The magazine goes on to report that Bartlett warns small nations could use the weapon against the Smart Grid, when it is developed: All one needs to wreak some serious EMP damage, he charges, is a sea-worthy steamer, $100,000 to buy a scud-missile launcher, and a crude nuclear weapon. Then fling the device high into the air and detonate its warhead.
Such a system might not paralyze the entire United States, he concedes. But you could shut down all of New England. And if you missed by 100 miles, it's as good as a bulls eye.
At the hearing, various people testified about how the grid might be hardened against attack, by protecting key components of it. Bartlett, though, isn't convinced that we're doing enough and wants EMP protection built directly into it.