The ultimate threat is that the industrial control systems that help operate the electric power system will be physically damaged. We saw examples of how this can happen in the Aurora test conducted at the Idaho National Laboratory. It is possible that physical effects can be created by computer attacks. The risk of physical damage on a widespread basis, that's frightening because of the difficulty of replacing some of these grid components. That's important.
Let me emphasize also that corrupting the data on which grid operators depend in order to restore power after an outage provides an additional emerging threat vector. As you know, grid operators need to carefully balance the amount of power that's being generated against the load, that is, the amount of electricity that's being used. This needs to be carefully calibrated. If grid operators can't believe the data they're seeing because the data itself has been attacked, that's just as devastating as a bank or another financial institution not being able to prove that your bank account is what it is.