Cybergeddon Looms Large
Secretary of Homeland Security Janet Napolitano was refreshingly (surprisingly) frank in her recent comments at the Wilson Center think tank in Washington, DC: "We shouldn't wait until there is a 9/11 in the cyber world. There are things we can and should be doing right now that, if not prevent, would mitigate the extent of damage." She indicated her feeling was that such an attack was imminent. It's not only a US concern, Australia's Prime Minister also just said much the same thing regarding their preparedness.
What are the risks of such a thing - either a physical attack such as an EMP, or a concerted and concentrated "hack attack"? I would say high, particularly for the latter scenario. The risks far outweigh the advantages for a potential attacker; the US in particular would make a wonderful "trophy", and the attackers can work away diligently and unmolested in dimly-lit buildings somewhere in the gulags, until their goals are realized. Time and effort can overcome almost any obstacle.
There are many such avenues for a non-physical attack, such as the SCADA control systems, long recognized as a ticking time bomb. Power generation, water treatment and other critical infrastructure could be crippled - and it would not need to be for very long to cause substantial pain, if the past experiences of winter storm damage is any measure.
Attacks on the financial sector could be just as devastating; we are trying to claw our way out of an extended recession are are still financially weak at the knees - consider how triggering a stock market crash might pull the rug out from under us. Financial transactions are almost entirely reliant on networks and digital transfers, very little currency is involved and so the digital devastation would be just as "real" as stealing truckloads of cash.
Unfortunately, I think the incidents we already see today are just the first waves lapping at the shore prior to the tsunami to come.