Specifically, the link network was trying to artificially inflate the PageRank and trust factors of websites through buying, selling and trading links with the sole intent of ranking higher in Google’s search results.
The translated version, via Google Translate, of the blog post reads:
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.
The last time Google officially confirmed hitting a link network with a penalty was back in November 2014, when Google targeted a Polish-based link network. Google did take action on many link networks back in 2014 but has focused more of their attention, at least communication-wise, on mobile spam and redirects.
You can see more of our coverage on Google Penalties over here.