Cloaking is a Black Hat SEO Technique and its very harmful for website.

Cloaking is a Black Hat SEO Technique and its very harmful for website.

Cloaking is a SEO tactics in which the content presented to the search engine spider is different from that presented to the user's web browser. This is done by delivering content based on the IP addresses or the User-Agent HTTP header of the user requesting the page. When a user is identified as a search engine spider, a server-side script delivers a different website pages version, one that contains content not present on the visible page, or that is present but not searchable. The motive of cloaking is sometimes to deceive search engines so they display. 

The Main Aim and Motive of Using Cloaking Technique

Websites Based on Flash Technology

There are lots of websites that are built in flash only. As you may know, flash is not good for Search engine optimization purposes. However, companies don't want to reconstruct their websites and rewrite everything in plain HTML. So they create content rich web pages and provide them to SEs and flash pages to visitors. (Note that Google has already started indexing sites in plain flash, but many other search engines still don't)

Photo Gallery Websites
photo gallery websites obviously have more photo’s than the actual content on their pages. So, webmasters think that cloaking could help them get top placement for keywords like "photo gallery".

HTML Rich Websites
SEO Specialist suggest having less HTML code and more genuine text on your Web pages. Sometimes, source code takes 94% or 97% of the whole web page's content. In order to avoid redesigning every web page, webmasters discover a much easier solution - cloaking

How is Cloaking Actually Done?

Now you know why, it's time to find out how. A cloaking is done by modifying a file known as .htaccess. Apache server has a module called "mod_rewrite". With the help of this module in .htaccess file you can apply a cloaking technique for your website pages.
 
Webmasters gather search engines' IP addresses (231.258.476.13) or User-Agents (Google Search Engine). If mod_rewrite module detects that an IP address or user-agent belongs to a search engine, it delivers a web page that is especially designed for SEs. If IP addresses doesn’t belong to any spider, than it thinks it's a regular visitor and delivers a normal web page.

Matt Cutt Cloaking Tutorial: