Link spam is defined as links between pages that are present for reasons other than merit. Link spam takes advantage of link-based ranking algorithms, which gives websites higher rankings the more other highly ranked websites link to it. These techniques also aim at influencing other link-based ranking techniques such as the HITS algorithm.
Link spam (also called blog spam or comment spam) is a form of spamming or Spamdexing that recently became publicized most often when targeting weblogs (or blogs), but also affects wikis (where it is often called wikispam), guestbooks, and online discussion boards. Any web application that displays hyperlinks submitted by visitors or the referring URLs of web visitors may be a target.
Link spamming originally appeared in internet guestbooks , where spammers repeatedly fill a guestbook with links to their own site and no relevant comment to increase search engine rankings. If an actual comment is given it is often just "cool page", "nice website", or keywords of the spammed link.
Link spam is a form of spamdexing. It is done by automatically posting random comments or promoting commercial services to blogs,wikis,guestbooks,or other publicly accessible online discussion boards.Google pushed the Penguin update for its algorithmic filter to lower the rankings of sites who use false measures to gain higher ranks in Google search results.Google has been working on some new algorithms and tools to tackle linkspam.