Step-by-Step Link Spam Recovery: How to Regain Your Rankings Fast

https://www.scribd.com/document/1032006019/Why-Parasite-SEO-Results-Vary-So-Much-Across-Different-Niches-154155

You do not “accidentally” wake up one morning and lose 30 to 80 percent of your traffic. Most of the time, it is link spam, or the kind of links that look like link spam to Google’s systems