But how does the internet cable get into your basement?

If your area uses underground cables then they might have to dig to cut your internet; it would take time but they wouldn't have to breach your property to do it. But many places use the existing overhead cable infrastructure to deliver internet, which are far easier to cut in an attack scenario. Or they could just attack the local exchange point, it's not as direct but it's nowhere near your house.

And in any case it may be easier to just cut the power. Your laptop or mobile phone have battery power but your modem or router probably don't.

Sleep tight.