Link spam
Google's spam policy category covering links intended to manipulate rankings: buying or selling links, excessive exchanges, automated link…
LinksLink networkLink wheel
Link farm
A group of sites that link to each other extensively for the sole purpose of inflating link counts, with no editorial reason for the links.
In full
Link farms predate PBNs and are cruder: dense reciprocal interlinking, often automated, sometimes sold as directory or 'web ring' membership. They are among the easiest patterns for link-analysis systems to identify because organic link graphs are not densely reciprocal. Modern variants include paid directory networks and automated comment or profile link systems.
Example
A directory sells membership that automatically adds every member's link to every other member's footer.
Related terms
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…
Reciprocal links
Two sites linking to each other; unremarkable when it reflects a real relationship, a link spam violation when exchanges are excessive or…
Link graph
The network of all pages as nodes and hyperlinks as edges, over which link-based ranking algorithms such as PageRank are computed.
SpamBrain
Google's AI-based spam prevention system, used to detect spam at crawl and ranking time and to identify and neutralise unnatural links.