E-mail spam is probably the kind of spam most users have encountered. It is simply junk mail that tries to deceive you into sharing personal details, or redirects you to a website containing malicious content.

Spamdexing is a kind of Black Hat SEO (Search Engine Optimisation) that manipulates the prominence of certain websites when using a search engine. It can be divided into Content Spam and Link Spam.

The content spam technique involves changing the way a search engine reads web pages in order to make a page more popular in searches. Keyword stuffing, Hidden text, Meta tag stuffing, Doorway Pages and Scraper sites are all kinds of Content Spam.

Keyword or Meta Tag Stuffing: This involves loading a web page with carefully chosen keywords that will increase the website's popularity when one of those keywords is searched for. These words can be placed in the actual content of the page or in its Meta Tags.

Hidden Text: This kind of search engine manipulation requires text to have the same colour as the page's background, thus making it invisible. This text may not be visible by visitors, but it is read by search engines and can lead to an increase of the website's popularity.

Doorway Pages: These are pages specifically created for spamdexing. When they come up as a search result and someone visits them, they automatically redirect the visitor to a different page using some kind of Cloaking technique, i.e. showing different web pages to human users and search engine bots.

Scraper Sites: These are websites that copy the content of other websites using the illegal technique of web scraping. Most of them make a profit out of this by loading their page with advertisements which visitors can click on. These are also known as Made For AdSense (MFA) websites.

Link spam manipulates rating algorithms, such as Google's PageRank, in order to promote certain websites. Types of Link Spam include Link Farms, Hidden Links, Page hijacking and Google Bombs. More specifically:

Link Farms: Also known as spam blogs, they are groups of websites that link to one another, in order to increase their popularity in search engines.

Hidden Links: Similar to the Hidden text technique, they are links placed in obscure locations of a web page so that visitors will not see them. This is beneficial because highlighted text ranks higher than normal text in search engines.

Page Hijacking: Also known as Typosquatting, this involves buying domain names that are very similar to those of very popular websites (e.g.: "www.gooogle.com", "en.wiipedia.org" etc) so as to make their page rank higher every time a user accidentally visits their page. A lot of the time the victim websites will try and pay the scammers off, which could have been their intention all along. Very few cases have reached the courts.

Google Bombs: Another kind of manipulation of Google's PageRank algorithm. This involves a lot of websites using consistent anchor text in order to link a virtually irrelevant website to a web search. The first example of this was one that caused the search term "more evil than Satan himself" to produce Microsoft's home page as the highest ranked result.