Link Spamming : King of black hat techniques, link spamming is just a way getting links to the websites of your choice through the use of automated software which accesses unprotected blogs through anonymous web proxies and leaves links in their comments. Long, frequently updated lists of proxy IP addresses are necessary, as well as decent comment generation software. Blog software developers have fought back, however, such as the the development of the Askimet comment filter for WordPress.
Splogs : Close cousins to scraping and spinning, splogs are simply blogs with worthless, automatically generated content. Many splogs read RSS feeds and create blog posts for themselves from them. Splogs are the framework into which scraped and spun content is laid out to create made-for-Adsense (MFA) sites. Also, splogs can be used to get other sites indexed or their Pagerank increased, by including links to them. A large percentage (some say 20% or higher) of the blogs on the web are actually splogs.
Scraping and Spinning : Scraping and its cousin spinning are a black hat technique that uses software to spider websites, grab the content, mix it up a bit, paraphrase, randomize, and generate “new” content from it. Often it will contain links to sites the marketer is trying to promote. Or, it will contain Ad-sense or other ads which are used to monetize the content. Spinning content into duplicate-content-penalty-avoiding text is the holy grail of black hat techniques. Programmers who come up with methods for doing this on-the-fly have created true money machines for themselves.
302 Redirect Hijacking : This technique is a really nasty black hat trick where the evil webmaster creates a web page on a high-page-rank domain with a 302 redirect to the page he is trying to hijack. Google-bot (or another search engine spider) follows the redirect to the second page and indexes it, but on the SERP, the URL of the indexed page will be that of the page with the redirect. In other words, the evil black hat webmaster will own the SERP, and the page with the content will be De-indexed. A truly evil hijacker builds cloaking into the redirect so human visitors to the page will go to his “money page”, while search engine spiders will still see the 302 redirect.
XSS Injection : Cross-Site Scripting (XSS) is a technique used to take advantage of certain pages with a special security flaw. They accept input from the HTTP GET request and display it on the page. Therefor, it is possible to construct a URL to one of these pages which will be displayed as a link to the site you specify, with the text you specify as the link text. The constructed URL can be set up as a link somewhere that a search engine spider will follow, getting the XSS-generated page indexed. Very sneaky.
Web Page Cloaking : This technique goes hand-in-hand with the doorway pages technique. The idea behind cloaking is to show a doorway page to search engine spiders but the “money page” to human visitors. Both pages are accessed using the same URL. Software is used to identify the search engine spiders and serve the doorway page to them. There is a dual purpose to web page cloaking: competitors are kept from scraping the content of the optimized doorways, and human visitors are kept from seeing the ugly doorway pages (the redirect is unnecessary in a properly executed cloaking solution).
Doorway Pages : Doorway pages are web pages created solely for the purpose of being spider-ed by search engines and included in the search engine results pages (SERPs). They are usually optimized for placement in the SERPs by being stuffed with keywords and created in bulk. Often, you will see that the pages are named after the primary keyword being targeted. Also, doorway pages will likely have a form of redirection involved sending visitors to the “money site”. The redirection can be a meta refresh tag or java script. Most webmasters using this technique will have software which cranks out doorway pages by the thousands.
Keyword Stuffing/Hidden Text : This technique involves picking a bunch of keywords for which a marketer wants a page to be optimized, and then placing them on the page in such a way that they will be read by search engine spiders, but not by human visitors. They can be located in a hidden div tag, colored so that they blend into the background, or even placed within HTML comment tags. This is truly an old school technique, and is not nearly as effective now as it was back in the day.
Cyber Hoaxing : Hoaxing is a way of “creatively” making news. First, create a fake news website that looks real. Second, write a sensational but false news story. It helps if it is difficult to prove the veracity. Third, create multiple accounts on various social networking sites such as Digg, StumbleUpon, Del.ico.us, etc., and submit your story there. Fourth, be ready for emails and phone calls from actual big-time media outlets with questions about your story. You will generate buzz and get links to your fake news story. Eventually, when it is discovered your story is false, try to capitalize on the outrage. How you monetize the whole situation is up to the webmaster, but it is commonly done with affiliate programs.
Buying Links : Is buying links a black hat technique? Of course it is. When a marketer pays for a link, they are essentially “buying a vote” for the page they are promoting. That link would not exist except that it was paid for. This gives extra weight to the promoted page in the search engine algorithms. The paid-for link does not itself add extra value to visitors, so the technique must be black hat.