Manufacturing Link Popularity

Some link popularity techniques are aimed at improving your business. Others are aimed at destroying a competitors brand or search engine rankings.
Redirect Hijacking Using a 302 redirect from a higher PageRank site you can wipe out a competitor with a lower PageRank.
Sending Bad Karma Some webmasters meta refresh the popularity of banned domains at their competitors domains.
Blogspam Some people use cheap Indian labor to spam comments on blogs, like "nice blog - phentermine viagra texas holdem poker 123". Others use automated bots and open proxies to blogspam. Sometimes people blogspam for a competitor to try to ruin the competitors brand.
Too Much Similar Anchor Text If your anchor text profile is not well mixed your site might be removed from the search index for popular queries. Some people have been known to use many sitewide same anchor text links to point at a competing site to prevent their competitors from ranking in Google for their most important terms.
Community Link NetworksMany community programs work to trade on site size, authority, PageRank, or money, as a currency to gain links from other sites which may not be on topic. Some of these networks can build thousands of links virtually overnight. This can lead to high rankings quickly in some engines, but rapid link bursts which fluctuate may lead to a site being filtered or penalized.
Email Spam Lots of high margin sites spam unknowing new webmasters asking for link exchanges. Some people may also spam for a competitor to try to destroy their brand.
3 Way Link TradeSome people set up bunk sites and have you link to their high profit site that does not link out to anything. In exchange they give you a link from a site that may be willing to link to anything to try to build linkage data into the main site. Some three way link trades are legit, but many are not.
Link Farms, Forum Spam, Guestbooks & DirectoriesSome people use cheap labor or bots to spam forums and guestbooks. Many directories have no quality standards and will link to anything. Many greedy directory owners have started numerous directories in an attempt to cash in on the directory craze. Link farms are often similar to directories that do not have quality standards although many link farms may be a bit more incestuous with more cross linking.
Random LinksLinks are nothing more than a citation. If you can think of things you can say, think, or do to make people want to link at your site you can build links. There also might be ways to automate portions of the process using software or social engineering. Well what about quality links

SEO Propaganda

One of the quietest forms of so-called "dark" SEO is rumor mongering. By creating an appearance of authenticity for a particular tactic or method, an SEO can influence lesser SEOs to pursue that tactic. This is especially effective on new or part-time SEOs. In a competitive world, such diversions can secure exlusive access to opportunities, and can be very lucrative.
Take for example public "SEO Guidelines" including such things as ebooks, webpages, open forums, and wikis. By aggregating a community of self-proclaimed SEOs to contribute articles and "expert content", one creates an appearance of authority. Contributors are anxious to add content, because it provides them with some external validation as "knowledgable SEOs", visible to the uninformed public. Consequently that consuming public, including wanna-be SEO webmasters, are deceived into believing that the tactics and methods so publically documented are accurate and complete.
In fact the real competitive tactics are absent from such publications, due to the simple fact that public disclosure would promptly render them ineffective. The consuming public is blind to the inherent sampling bias of the wiki (no real SEO secrets, no real competitive advantages). In some extreme cases, SEOs may publish such public SEO documents for the "public good" only until they are content-rich and popular among the naive, at which point the owner can slap ads all over it and monetized that free content for personal gain. Professional SEOs are wise enough to always inspect disclaimers  and copyright statements  before contributing, to be sure they are professional, fair, and equitable.

Spamdexing

Spamdexing is any of various methods to manipulate the relevancy or prominence of resources indexed by a search engine, usually in a manner inconsistent with the purpose of the indexing system. Search engines use a variety of algorithms to determine relevancy ranking. Some of these include determining whether the search term appears in the META keywords tag, others whether the search term appears in the body text or URL of a web page. Many search engines check for instances of spamdexing and will remove suspect pages from their indices.
The rise of spamdexing in the mid-1990s made the leading search engines of the time less useful, and the success of Google at both producing better search results and combating keyword spamming, through its reputation-based PageRank link analysis system, helped it become the dominant search site late in the decade, where it remains. Although it has not been rendered useless by spamdexing, Google has not been immune to more sophisticated methods either. Google bombing is another form of search engine result manipulation, which involves placing hyperlinks that directly affect the rank of other sites[1]. Google first algorithmically combated Google bombing on January 25th, 2007.
The earliest known reference to the term spamdexing is by Eric Convey in his article "Porn sneaks way back on Web," The Boston Herald, May 22, 1996, where he said:
The problem arises when site operators load their Web pages with hundreds of extraneous terms so search engines will list them among legitimate addresses. The process is called "spamdexing," a combination of spamming — the Internet term for sending users unsolicited information — and "indexing."[2]
Common spamdexing techniques can be classified into two broad classes: content spam and link spam.

Content spam

These techniques involve altering the logical view that a search engine has over the page's contents. They all aim at variants of the vector space model for information retrieval on text collections.
Hidden or invisible text:

• Disguising keywords and phrases by making them the same (or almost the same) color as the background, using a tiny font size or hiding them within the HTML code such as "no frame" sections, ALT attributes and "no script" sections. This is useful to make a page appear to be relevant for a web crawler in a way that makes it more likely to be found. Example: A promoter of a Ponzi scheme wants to attract web surfers to a site where he advertises his scam. He places hidden text appropriate for a fan page of a popular music group on his page, hoping that the page will be listed as a fan site and receive many visits from music lovers. However, hidden text is not always spamdexing: it can also be used to enhance accessibility.

Keyword stuffing:

• This involves the calculated placement of keywords within a page to raise the keyword count, variety, and density of the page. Older versions of indexing programs simply counted how often a keyword appeared, and used that to determine relevance levels. Most modern search engines have the ability to analyze a page for keyword stuffing and determine whether the frequency is consistent with other sites created specifically to attract search engine traffic.

Meta tag stuffing:

• Repeating keywords in the Meta tags, and using keywords that are unrelated to the site's content, believed to be ineffective as of 2005 onwards.

"Gateway" or doorway pages:

• Creating low-quality web pages that contain very little content but are instead stuffed with very similar key words and phrases. They are designed to rank highly within the search results, but serve no purpose to visitors looking for information. A doorway page will generally have "click here to enter" in the middle of it.

Scraper sites:

• Scraper sites, also known as Made for AdSense sites, are created using various programs designed to 'scrape' search engine results pages or other sources of content and create 'content' for a website. The specific presentation of content on these sites is unique, but is merely an amalgamation of content taken from other sources, often without permission. These types of websites are generally full of advertising, or redirect the user to other sites.

Link spam

Link spam takes advantage of link-based ranking algorithms, such as Google's PageRank algorithm, which gives a higher ranking to a website 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 farms:

• Involves creating tightly-knit communities of pages referencing each other, also known humorously as mutual admiration societies

Hidden links:

• Putting links where visitors will not see them in order to increase link popularity.

"Sybil attack":

• This is the forging of multiple identities for malicious intent, named after the famous multiple personality disorder patient Shirley Ardell Mason. A spammer may create multiple web sites at different domain names that all link to each other, such as fake blogs known as spam blogs.

Wiki spam:

• Using the open editability of wiki systems to place links from the wiki site to the spam site. Often, the subject of the spam site is totally unrelated to the page on the wiki where the link is added. While many powerful tools exist to filter or block email spam, there are very few tools for blocking wikispam.

Spam in blogs:

• This is the placing or solicitation of links randomly on other sites, placing a desired keyword into the hyperlinked text of the inbound link. Guest books, forums, blogs and any site that accepts visitors comments are particular targets and are often victims of drive by spamming where automated software creates nonsense posts with links that are usually irrelevant and unwanted.

Spam blogs (also known as splogs):

• A spam blog, on the contrary, is a fake blog created exclusively with the intent of spamming. They are similar in nature to link farms.

Page hijacking:

• is achieved by creating a rogue copy of a popular website which shows contents similar to the original to a web crawler, but redirects web surfers to unrelated or malicious websites.

Referer log spamming:

• When someone accesses a web page, i.e. the referee, by following a link from another web page, i.e. the referer, the referee is given the address of the referer by the person's internet browser. Some websites have a referer log which shows which pages link to that site. By having a robot randomly access many sites enough times, with a message or specific address given as the referer, that message or internet address then appears in the referer log of those sites that have referer logs. Since some search engines base the importance of sites by the number of different sites linking to them, referer-log spam may be used to increase the search engine rankings of the spammer's sites, by getting the referer logs of many sites to link to them.

Buying expired domains:

• Some link spammers monitor DNS records for domains that will expire soon, then buy them when they expire and replace the pages with links to their pages.

Some of these techniques may be applied for creating a Google bomb, this is, to cooperate with other users to boost the ranking of a particular page for a particular query.

Other types of spamdexing

Mirror websites:

• Hosting of multiple websites all with conceptually similar content but using different URLs. Some search engines give a higher rank to results where the keyword searched for appears in the URL.

URL redirection:

• Taking the user to another page without his or her intervention, e.g. using META refresh tags, Java, JavaScript or Server side redirects

Cloaking refers to any of several means to serve up a different page to the search-engine spider than will be seen by human users. It can be an attempt to mislead search engines regarding the content on a particular web site. However, cloaking can also be used to ethically increase accessibility of a site to users with disabilities, or to provide human users with content that search engines aren't able to process or parse. It is also used to deliver content based on a user's location; Google itself uses IP delivery, a form of cloaking, to deliver results.
A form of this is code swapping, this is: optimizing a page for top ranking, then, swapping another page in its place once a top ranking is achieved.
The following techniques are also widely acknowledged as being spam, or "black hat":

• Doorway pages
• Link farms
• Googleating

How Not To Promote Your Web Site

Beginners have a tendency to try to get their link on as many pages as possible, without putting much thought into it. A lot of this can be classified as spam. This consists of joining a forum or blog, and posting a message about your new web site and it's url. While your intentions may be good, this will undoubtedly upset everyone on the forum or blog, and force the maintainers to simply delete your message, before it ever becomes an effective link picked up by the search engines.
The proper way to obtain links is to actively seek them at sites where link submittal is encouraged, such as directories

 

References

1. Deconstructing Google bombs
2. Word Spy: spamdexing