if specialized teams can find terrorits on the internet?

[DunbarPappy®ϟϟ]

Here's an article about finding the troublemakers:
Google highlights trouble in detecting web-based malware
https://www.computerworld.com/s/article/...geNumber=1
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They do get 'backdoors':
NSA pay to put a backdoor in RSA crypto; http://www.theregister.co.uk/2013/12/21/...0_million/
And Snowden revelations hint at major vendors who were approached by NSA (et al) to do clandestine spying...and compelled to not mention it by virtue or the Patriot Act Gone Wild.
Microsoft complicit with NSA; adding 'backdoors' to many services; http://www.theregister.co.uk/2013/07/11/..._for_feds/
(There are many hints of several vendors having been 'approached', so MS is not an isolated incident.)
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Forcing a global 'shutdown' (even temporary) of the 'Net is beyond practical.
Different governments have their own agenda's and all seek self-serving objectives, and they control their own 'backbone' servers.
Random, sporadic isolations would solve nothing: the architecture of TCP/iP assures that packets will eventually make their way to the destination, by moving thru alternate 'best effort' routes.
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Not sure what your last idea conveys.