Risks to under-sea cables? - NOT amateur radio

Much of our internet, banking and commercial traffic is carried on undersea cables and fibre. Apparently the military is worried by the vulnerability of such cables to rogue nations intent on disruptive warfare. The internet is a distributed system, so unless lots of lines are cut, it is unlikely to break completely, although traffic could be slowed.

I am not quite sure how you can protect these cables. It needs a nation with submarines to be a real threat.

See http://www.bbc.co.uk/news/uk-42362500 .