http://www.reuters.com/article/2010/03/11/urnidgns852573c400693880852576e-idUS222688325020100311
http://www.wwlp.com/dpp/news/wwlp_local_cyber_attacks_plague_govt_websites_20090709
http://www.geopoliticalmonitor.com/south-korea-hit-by-cyber-attack-2357/
http://www.fresnobee.com/2011/02/02/2257241_hackers-attack-egyptian-govt-sites.html
About us: http://www.pcworld.com/article/164092/panel_calls_for_national_dialog_on_govt_cyberattacks.html
Not meaning to overemphasize the possibility, but: http://tinyurl.com/ygcmh9b
They're not the only ones capable.
Oh, yeah, some kids like to knock down web sites here and there. So what? Such 'attacks' on govt web sites happen all the time and present no real threat to anything. Moreover, intent of such 'attack' is to either raise attention (like anons do) or make information unaccessible. By disabling national internet, you are just doing what attackers are trying to - you disable ALL these sites yourself.
As for espionage, in most cases it is done via malware, and disabling internet will be no help these, as target computers are not connected to internet anyway, and malware is designed to spread via flash drives and other means.
I did waste some hours reading that report, but still do not see how it justifies Internet lockdown. Text mostly is too vague to properly understand what kind of threats they are talking about, and I'm suspecting its primary intent is to give false impression of China's IW offencive capabilities to report readers.
I'm not saying IW does not exist. But its nature is far from what journalists and such Krekel's are drawing to the public. There are no 'attack dates', there is long-term, routine work, which can be countered only by according enforced security policies.