Black hat SEO is a practice against search engine guidelines, used to get a site ranking higher in search results. These unethical tactics don't solve for the searcher and often end in a penalty from search engines. Black hat techniques include keyword stuffing, cloaking, and using private link networks. The term "black hat" originated in Western movies to distinguish the "bad guys" from the "good guys," who wore white hats.

The following are black hat techniques:

Keyword Stuffing

It takes you nowhere. Google can easily trap the unnecessary proliferation of keywords and lower the ranking. Examples of keyword stuffing include:

  • Lists of phone numbers without substantial added value
  • Blocks of text listing cities and states a webpage is trying to rank for
  • Repeating the same words or phrases so often that it sounds unnatural, for example: "We sell custom product abc. Our custom product abc are handmade. If you’re thinking of buying a custom product abc, please contact our custom product abc specialists at custom.product.abc@example.com".

Cloaking

The dangerous sin that Google comes against heavily. Do not indulge in any technique that may even vaguely come close to cloaking.

Scraped Content

Purely scraped content, even from high-quality sources, may not provide any added value to your users without additional useful services or content provided by the site; it may also constitute copyright infringement in some cases, and Google hates it.

Link farms

or any link-scheme to artificially spawn off backlinks – Google can easily detect any unnatural or unrelated links and penalize.

Sneaky Redirects

This is similar to cloaking. There are many good reasons to redirect one URL to another, for example when moving your site to a new address, or consolidating several pages into one. Sometimes, redirects are designed to deceive search engines or to display different content to human users than what the search engines crawl and index. It’s a violation of Google’s Webmaster Guidelines to use JavaScript, a Meta refresh, or other technologies to redirect a user to a different page with the intent to show the user a different page than a search engine crawler sees. However, to speak broadly, using JavaScript to redirect users can be a legitimate practice. In evaluating whether it is sneaky or not, the perceived intent is very important and Google can evaluate that. For example, if you redirect users to an internal page once they’re logged in, you can use JavaScript to do so. Keep in mind that 301 redirects are best when moving your site, but you could use a JavaScript redirect if you don’t have access to your website’s server.

Hiding text or links

Hiding text or links in your content to manipulate Google’s search rankings can be viewed as deceptive. Google is well aware of the black-hat practices like including:

  • Using white text on a white background.
  • Locating text behind an image.
  • Using CSS to position text off-screen.
  • Setting the font size to 0.
  • Hiding a link by only linking one small character—for example, a hyphen in the middle of a paragraph.

Auto-generated content

One of the risky SEO practices is automatically generated contents, spawned off programmatically, generally consisting of paragraphs of random text that makes no sense to the reader but which may contain keywords. Some examples of auto-generated content, according to Google, include:

  • Text translated by an automated tool without human review or curation before publishing.
  • Text generated through automated process, such as Markov chains
  • Text generated using automated synonymizing or obfuscation techniques.
  • Text generated from scraping Atom/RSS feeds or search results.
  • Stitching or combining content from different web pages without adding sufficient value.

Malicious Contents

Let me quote from Google’s own resources on what they consider as malicious. ”Distributing content or software on your website that behaves in a way other than what a user expected is a violation of Google’s Webmaster Guidelines. This includes anything that manipulates content on the page in an unexpected way, or downloads or executes files on a user’s computer without their consent. Google not only aims at returning the most relevant search results for the queries, but also to keep the web-experience safe on web. Some examples of malicious behavior include:

  • Changing or manipulating the location of content on a page, so that when a user thinks they’re clicking on a particular link or button the click is actually registered by a different part of the page
  • Injecting new ads or pop-ups on pages, or swapping out existing ads on a webpage with different ads; or promoting or installing software that does so
  • Including unwanted files in a download that a user requested
  • Installing malware, trojans, spyware, ads or viruses on a user’s computer
  • Changing a user’s browser homepage or search preferences without the user’s informed consent."