Spamdexing, also known as webspam or black-hat SEO. Spam index means the usage of manipulative designs to fool or manipulate the search engines and boost the ranking artificially for some time. These techniques contravene the injunction laid down by the search engines and are not of any effective use. This led search engines like Google to actively suppress. 

Websites that take advantage of SEO tactics to get a higher ranking on searches are considered spamdexing. 

Common Spamdexing Techniques.

Spamdexing sort of has two varieties content spam and link spam.

Content Spam

• Low-Quality Auto-Generated Content Designed for Algorithms, Not Users
• Thin content refers to pages that provide little or no value to the user.
• Cloaking refers to the practice of showing different content to the search engines than what is shown to the users.
• Hiding text that has keyboard stuff in it or is not visible. It should be avoided.
• Doorway pages are purposely created low-quality pages that only rank for particular queries.
• Republishing content from other sites without adding any value. 
• Overloading a web page with excessive keywords, especially irrelevant ones.

Link Spam

• Make a private blog network of sites like that to give links to you.
• Paid links – Buying backlinks to boost website authority.
• Doing too many guest posts and exchanging links – This is link-building that does not add any value.
• Acquiring old domains just for their backlinks is expired domain abuse.
• Posting spam links in forums, blog comments, and profiles is a form of spam. 
• Hacked links mean injecting backlinks to hacked websites or ones not under the guidelines of the user.