Search giant Google (GOOG) said it has revised its search algorithm to filter bad sites after a New York Times article exposed how an online merchant manipulated Google to get publicity for his website.

The latest development comes as European Union has decided to probe Google after complaints by search service providers about unfavourable treatment of their services in Google's search results. There were also allegations that Google meted out preferential placement of its own services to shut out competing services.

On Nov.26, The New York Times published an article in which Vitaly Borker, who owns website, described how he used negative feedback on Google and on other sites to boost his site's rankings in the Google search results, which yielded him more revenues. The main premise of that article was that being bad on the web can be good for business.

Borker claimed to the paper that he deliberately shouted at and frightened some of the customers at as the online complaints actually worked in his favor in Google search results. He also claimed that Google's search engine is unable to tell the difference between positive posts and withering online.

Responding to the article, Google said Wednesday that it had revised its search engine rankings that will make unscrupulous traders harder to appear prominently in searches.

We can say with reasonable confidence that being bad to customers is bad for business on Google, Amit Singhal, a Google Fellow, wrote in a blog post that said Google was horrified by the story.

Even though our initial analysis pointed to this being an edge case and not a widespread problem in our search results, we immediately convened a team that looked carefully at the issue. That team developed an initial algorithmic solution, implemented it, and the solution is already live, Singhal wrote.

Singhal said Google has considered various alternatives to the issue, including blocking the particular offender. But it discarded the solution thinking that blocking the offender wouldn't solve the larger issue in a general way.

Google said its another option was to use sentiment analysis to identify negative remarks and turn negative comments into negative votes. But Google discarded this alternative also, saying if it demoted web pages that have negative comments against them, users might not be able to find information about many elected officials, not to mention a lot of important but controversial concepts.

So far we have not found an effective way to significantly improve search using sentiment analysis. Of course, we will continue trying, Singhal added.

Instead, Google said it has solved the issue by making certain changes in its search algorithm and Singhal said it represents an initial solution to this issue, and Google users are now getting a better experience as a result.

Our first reaction in search quality is to look for ways to solve problems algorithmically, Singhal wrote in the blog post.

However, Google refused to divulge the details of changes it made in its search rankings as it will allow unscrupulous people to take advantage of the system.

We can't say for sure that no one will ever find a loophole in our ranking algorithms in the future. We know that people will keep trying -- attempts to game Google's ranking, like the ones mentioned in the article, go on 24 hours a day, every single day. That's why we cannot reveal the details of our solution-the underlying signals, data sources, and how we combined them to improve our rankings-beyond what we've already said, Singhal said.