Spamdexing is a form of search engine manipulation which is designed to push a site up in search results, ensuring that people land on that site when they search for specific things. While search engine optimization requires a certain amount of search engine manipulation to ensure that sites rank high in search results, spamdexing is typically more offensive, and the material is less relevant to the search than the searcher might desire. Because many people become frustrated by constantly finding spam sites when they look for legitimate content, most search engines have tools in place to defeat spamdexing.
The term is a portmanteau of “spam” and “indexing,” and it started appearing in print in the late 1990s, when spamdexing started to become a major issue. In a way, spamdexing was the almost inevitable result of the rise of the Internet, as people began to realize that there was immense monetizing potential in websites, and spam began to proliferate not only in in-boxes, but on the web. The number of spam sites on the Internet is not fully known, but it is estimated to be an extremely high percentage of the Internet.
There are all sorts of ways to spamdex. For example, a site may be stuffed with keywords, even if the site does not actually contain material relevant to those keywords. Sites can also use hidden text, hidden links, and stuffed metatags to inflate their search rankings. Many spammers utilize multiple mirror sites, all with more or less the same content, but different web addresses, linking these sites to each other, and others use site redirects, which send users to a third party site.
When someone accesses a site which has been inflated with the assistance of spamdexing, he or she may find that the site contains complete gibberish, along with a number of advertisements. Spamdexed sites are also used to raise the relevancy ranking of other sites maintained by spammers. In some cases, such sites aren't even really meant to be seen by humans, as they exist solely to promote another website, taking advantage of search engine results which rely on authority and relevance as well as keywords.
In addition to being extremely annoying, spamdexing can also be dangerous. For example, someone could spamdex a site with the name of a major financial institution, creating a situation in which patrons of that institution would access the site, think it was their bank's site, and disclose personal information which could be used for identity theft, or at least to clean out their bank accounts.