Such a manipulation affects the credibility of the results displayed by the search engines. Hence it becomes imperative for them to find a way out so that such manipulated pages can be caught and penalized. When a site is penalized it is the biggest setback for a SEO services provider. Content filter is one such tool of search engines which helps them judge between genuine and fake content.
Duplicate content, the biggest nightmare for a SEO company can be created in many different ways as below:
Using lot many keywords in the same article
Creating similar pages thinking it would increase chances for inclusion in search engine listings
Creating two different pages one filled with useful content for the users and the other stuffed with keywords
Copying the same content on someone else's site on your own site
An important question popping up is how search engine filters duplicate content page to give the most relevant results to the users. Search engines maintain a database of all the websites on the Internet. The information for this database is gathered by the spiders which crawl through the different websites. When the spiders visit any new site a comparison of the content on the new site is made with that in the database. This makes it clear which pages are duplicate and which are genuine.
Often genuine sites fall prey to search engine filter. Still there are ways to save from it. The first step is to make sure if your site has any duplicate content and this can be done by using tools like Similar Page Checker. This will give you a clear idea if your content matches with any other site and if it is positive then you can amend the content before search engines can find about it.
In other case it is quite possible someone else might have copied your pages. To check on such sites we have a tool called copyscape.com. It is simple to use and very quick to display results. Just put in your website link and enter it will show all the matches if any found.