The major approach the search engines use is to design algorithms that can detect and act on link spam. There are a number of things they can look at algorithmically. Here are a representative few: Links labeled as advertisements the search engines can scan for nearby text, such as “Advertisement,” “Sponsors,” “Our Partners,” and so on.
Site-wide linking is unnatural and should be a rare part of your link mix (purchased or not). The only exception to this is the interlinking of all the sites owned by your company, but this presumes that the search engine will understand that all of your sites are from the same company. In general, sitewide links are a serious flag, especially if you have a lot of different sites that do this for you, or if a large percentage of your links are site-wide.
Pages), resulting in the company changing its stance on the subject.20 In February 2011, Google took action against J.C. Penney for buying links,21 and Conductor eventually exited the business of brokering buys.
A selling site providing information on how to buy a text link ad Search engines can detect sites that provide information on how to advertise with them. Combined with other clues about links being sold on the site, this could lead to a review of the site selling the ads and a discounting of the links.
Relevance of your link It is a powerful clue if your link is not really that relevant to the page or site it is on. Quality of neighboring links another clue would be the presence of your link among a group of links that are not tightly themed, or if the other sites linked to are poor quality. Location outside main content The search engine can detect when your link is not part of the main content of the page—for example, if it appears in the left or right column of a three-column site, and the main content is in the middle.22
Does someone report your site for buying links or for some other reason Who would do this? Your competitor! If your competitor submits an authenticated spam report to Google, Google will look at it and may choose to act on it. Someone reports the site you bought links from for selling links or for some other reason A competitor of yours can do this, or a competitor of the site selling links can do this. Once a search engine figures out that a site is selling links, it is possible that this could trigger a deeper review of the sites that were buying those links.
A disgruntled employee leaves your company, the broker, or the site you bought links from and reports your site For decades, many companies have had a practice of escorting fired (or laid-off) employees out of the building. The reason for this approach is that people get upset when they lose their job.
However, this practice would not prevent such a person from reporting your site in a spam report to a search engine. Even though that may be a violation of the confidentiality agreement you probably have with your employees, you would never know, because there is no transparency in spam reporting.