Scraper Sites
Perhaps the most pernicious of web spam techniques involves scraper sites. Instead of using a keyword list and an algorithm to generate content, scraper sites use the snippets displayed in a search results page. Scrapers visit the top 10, 20 or even 100 sites ranked for each key phrase and extract the content from those sites. The scraper may simply republish the content at another domain and try to earn rank or they may actually recombine the text they harvested into a creative (and frequently bizarre) collection of sentences and paragraphs.
Most scraper sites are “MFA” (Made for AdSense) sites intended to get users to visit and click on advertising. The scraped content is very low quality and generally redundant, since it’s content is derived from the top ranked pages and would have appeared had no MFA website been found in the listings.