Wie das mit den Netzsperren funktioniert, machen die USA und dort AT&T grade vor:
Firing one of the first shots in the net neutrality war, AT&T has blocked 4chan’s /b/ image board. AT&T subscribers are unable to connect to /b/ and /r9k/ (both of which are hosted on img.4chan.org). However, subscribers can get on any of the so-called «worksafe» boards that 4chan.org offers.
The problem seems to be present only for wired connections only (AT&T Mobility customers are not affected). The problem is not caused by an DNS-error, as traceroutes indicates that AT&T is dropping img.4chan.org requests in the AT&T network.
Und den Müll von diesem Herrn von den Grünen kommentiere ich nicht und verlinke das noch viel weniger, weil: Don't feed the trolls.
[update] Dirk schreibt mir: „Ich dachte, es wäre inzwischen rumgegangen: Grund ist wohl ein DDoS auf 4chan, deshalb wird bzw. wurde das wohl geblockt.“
There has been alot of customers on our network who were complaining about ACK scan reports coming from 18.104.22.168. We had no choice but to block that single IP until the attacks let up. It was a decision I made with the gentleman that owns the colo facility currently hosts 4chan. There was no other way around it. I'm sure AT&T is probably blocking it for the same reason. 4chan has been under attack for over 3 weeks, the attacks filling up an entire GigE. If you want to blame anyone, blame the script kiddies who pull this kind of stunt.