Link Farming – the Shadier Side of SEO
Any place where there is money is to be made, you can be sure that there is someone out there trying to game the system to their advantage—the internet is no exception. Where one’s website appears on search engine searches can make or break a business. Think about it—how often do you venture past the first page of a Google search? As a result, search engine optimization, the strategies and processes used to boost one’s position on the list of results returned by a search engine, has become a near-essential part of hosting a successful website. While SEO in and of itself is not exactly unethical, and most who use SEO do not there are definitely many “shady” SEO techniques employed by those who are less scrupulous . One such technique, link farming, exploits the theory behind Google’s PageRank algorithm to boost website rankings.
Google’s PageRank operates on the simple idea that the quality (i.e. higher quality, better search result ranking) of a website is measured by the amount of websites that link to it. But the quality of the linking websites matter as well! For example, a website is probably of higher quality if the New York Times links to it rather than IthacaSlowLorisEnthusiasts.com; the New York Times website quite obviously is of higher quality than the latter page, as it is linked to from a far greater amount of websites than the latter. Link farms exploit this idea. In the diagram below, we see the basic structure of a link farm—a group of websites that all link to each other—a clique, in graph theory.
As explained in the paper Identifying Link Farm Spam Pages by Wu and Davison, a link farm is “one example of tightly-knit community effect,” and “TKCs can have a significant effect impact on ranking results.” But link farms are differentiated from normal TKCs, in that the websites in the link farms contain large number of links to other websites without any structure or category organization. Linking to a website is effectively endorsing the quality of that website—clearly, link farms websites, which all link to each other, boost the quality of each of the individual websites. But all these websites are utilized for another purpose—endorsing (linking to) another website, the actual website that one wants to boost. By adding the new website into this clique, the PageRank algorithm can be ‘fooled’—since all these websites seem reputable and high quality (they all link to each other), if they all link to a new website, that website must be very relevant! So there are two parts to the Link Farm idea—linking many websites to one targeted website (the one you want to boost) increases the raw in-linkage to that page, boosting PageRank, and linking those many websites to each other boosts the ‘quality’ of their endorsements, as they appear more reputable.
Today, the effectiveness of link farming has largely been significantly reduced by the improvement of search engine intelligence—most search engines can now recognize and filter link farms from their searches (refer to the source below for some techniques—one technique uses the densely connected nature of link farms to identify them). Yet the war rages on against shady SEO—black hat SEO techniques, as a result of their lucrative nature, are like the heads of a hydra—eliminate one, and two more will emerge.
Source – Identifying Link Farm Spam Pages