So, I have been out of the blackhat SEO loop for the last 3 years. From my experience from several years back, true PBNs (a Private Blog Network that you setup for yourself and don't let others use) can work if you are careful about not leaving footprints. Also, contextual backlinks from authoritative sites also worked. So has anything really changed in blackhat SEO in the last few years? From my understanding, Google claimed they were going to shift more towards social signals but it seems that link building in 2019 is still more effective than social signals. Also, from what I have read so far, PBNs (that is, private ones that you setup for yourself to use only) are still effective. What else has changed in the last 3 years?