I've heard from some people that it could be lulzsec that is doing the DDoS.
They point to this as evidence:
http://pastebin.com/7K4DgwQc
I don't think it's them personally though... Why would they go after
4chan? Also a DDos isn't their normal MO. Normally they'd try to do
some kind of security exploit, instead of a brute force attack. Also
that pastebin could very easily be faked?
Other people have been saying that tumblr is behind this, but I reall,
really doubt that too. I just don't think they could pull something
like this off, especially for how long it's been going...
http://i.imgur.com/VLgde.jpg
Also this poster that they cite calls for the attack on Nov. 15th,
when the actual attack happeneda earlier than this.
http://news.cnet.com/8301-1009_3-57326177-83/4chan-outage-could-be-digital-version-of-a-food-fight/
^--- source on the tumblr
And that's all I've heard, save for some other crazy theories (MArk
Zuckerberg is doing it, the government is doing, the mexican cartels
doing it, etc)