clipped from: Here's a great example of how easy it is to disrupt critical infrastructure, without computer skills (which is one of the reasons I believe, based on a broad number of examples, it is a more useful method of warfare).
Vandals cut off cellular, Internet and landline phone service to 52,000 thousand people today in the San Francisco Bay area. Cables were cut in two places. Four ATT fiber optic cables were cut at 1:30 AM at a site adjacent to a highway/railroad and another pair (ATT/Sprint) were cut two hours later in a residential area. The operation was simple: lift a heavy manhole cover and cut the cables with a blow torch. As is the rule, nobody was caught, or likely to be caught.