Link spam
Google's spam policy category covering links intended to manipulate rankings: buying or selling links, excessive exchanges, automated link…
Algorithms
SpamBrain
Google's AI-based spam prevention system, used to detect spam at crawl and ranking time and to identify and neutralise unnatural links.
In full
Introduced publicly in 2018 and extended to link spam detection in the December 2022 link spam update, SpamBrain identifies both spammy sites and the sites linking to them, nullifying the credit those links pass. Google reports on its effectiveness in periodic webspam reports. Because it neutralises rather than penalises in most cases, the visible symptom is usually a loss of previously effective link value rather than a notification.
Example
After a link spam update, a site's paid link portfolio stops contributing and rankings settle back to their organic baseline.
Related terms
Penguin
Google's link spam algorithm launched in 2012; since version 4.0 in 2016 it runs in real time within the core algorithm and devalues spam…
Spam updates
Announced improvements to Google's automated spam detection, distinct from core updates, targeting violations of the spam policies.
Google spam policies
Google's documented list of behaviours that can cause lower rankings or removal, covering cloaking, doorways, hacked content, keyword…
Private blog network
A set of websites, often built on expired domains, controlled by one party for the purpose of passing links to money sites; a clear link…