The reason for the targeting was that the link network was trying to artificially inflate the PageRank and trust factors of websites through buying, selling and trading links with the intent of ranking higher in Google’s search results.
After translation via Google Translate, here’s what the blog post said:
As part of this effort, Google this time, in order to operate illegally search result link program has undergone a countermeasure against some of the site network of the Japanese had done the buying and selling of participating in the link. Among this is because it was also included sites that repeatedly Webmaster Guidelines violation, was subjected to severe measures than normal in some cases.
In addition, we tell even before, there seems to be the case that measures would be carried out, such as violation of the Webmaster Guidelines in place without the knowledge of the webmaster. Previously it introduced the example of SEO firms , but it seems there is also be generated by the outsourcing of such advertising not only SEO skilled in the art. In order to prevent this, the web master you we recommend that you check from time to time and see whether subcontractors are doing what measures.
It was back in November of 2014 when Google last confirmed hitting a link network with a penalty.