Google has published its webspam report for 2017. These are sites which abuse or violate its webmaster guidelines, and those that might have been hacked and infected with malware.
Google says it removed more than 80% of hacked sites from the SERPs last year.
The company also said it put greater effort into discovering and removing unnatural links through "ranking improvements" and "scalable manual actions," resulting in a year-on-year reduction of spam links by almost half. Just a guess, but I suspect they are using much more AI through machine learning to achieve this.
Users reported search spam almost 90,000 times, allowing Google to evaluate and act as required.
In 2017 it also sent 45 million messages to webmasters via the search console, with over 6 million of those related to manual actions.