Over the past few months, Google Analytics accounts have been increasingly spammed by sites like Event Tracking, Best SEO Solution, Social Buttons to name a few. The phenomenon is growing more and more and spam results in distorted statistics and the appearance of these spam sites in the referring sites, pages viewed, events etc.
There are methods for remove these spam sites from your Analytics reports and thus obtain more accurate statistics.
Here, in the form of an infographic, are the solutions for recognize spam sites and block them of your statistics.
The methods set out in the infographic are not the only ones that exist, of course, but they are among the most effective.
I recommend this very good article on the Referrer Spam (in English) long, but complete and regularly updated to go further and discover other methods to eradicate spam.