A link farm (also called link network) is a domain or website, which was specially created to provide links to other websites in order to influence the rankings for the linked webpages. Link farming accordingly denotes the accumulation of outbound links on a web page that reference many different websites or individual webpages.
Link farms are frequently used by website operators with the purpose of raising their websites as high as possible in search engine rankings.
Link farms are easily recognizable since they usually consist of a website with little content but a large number of external links that are sometimes located in the footer. The relevance of text content and HREF links play a major role, because search engines have the ability to identify link networks as such and take countermeasures. Link networks are regarded a violation of the search engine guidelines and will be penalized upon discovery. Link farming is black hat SEO.
Link farming is quite different from link building or web projects such as business or online directories. Of course links get generated here too. However, link building is the embedding of links in an editorial context, i.e. the combination of good content and quality references. Business or online directories are concerned with the collection of useful information which is used to get hard to find data that would otherwise have to be collected by the users themselves in elaborate Internet searches.
Link farms are often websites that do not contain any relevant content and only serve the purpose of link building. Websites that exclusively conduct link farming can also be referred to as a link network. Such sites are useless to visitors, because their sole purpose is to refer to other websites and thus increase their link popularity. They are supposed to increase the Page Rank based on the number of links which refer to the website in question.
Up until a few years ago, such methods worked, but the search engines are getting better at identifying spam, link networks, and other black hat methods to explore techniques such as cloaking. The use of link farms is targeted by Google and considered spam. If a link farm is detected, it will be listed far down in the search results or get removed completely from the search engine index and will therefore no longer be accessible to users.
Moreover, Google will penalize any other websites that were connected with such a link farm, because links from previously identified link networks are generally considered harmful. Google does not just evaluate the number of links, but also their quality. A senseless abundance of links that are in no way related to the content of the website get devalued by the search engines and will then negatively affect ranking.
As a consequence, the linked websites will slip down on the search result lists. This occurs quite regularly and website operators and agency clients are well advised to refrain from this type of Black Hat SEO or if necessary to inform their contracted agency that they desire natural link building. If you already have link farm links, they should be identified and removed. This requires first a detailed backlink analysis and then all malicious links have to be manually removed. A reconsideration request can subsequently be submitted to Google.