Jordan and others have written in about North Korea being offline.  Arbor has a great post with some analysis (http://www.arbornetworks.com/asert/2014/12/north-korea-goes-offline/). According to the article, the netblock that is being targted is 175.45.176.0 – 175.45.179.255.  For more detail follow the link above. 

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Tom Webb