Referrer spam is a kind of spamdexing which is aimed at search engines such as Google (More Information). Do you often see referring sites in your Google Analytics with many sessions but a Bounce Rate close to 100%? Chances are these are spam links. While this does not inherently hurt your site (afterall they are not even real visits to your site), they do skew the traffic data (direct traffic, referral traffic) and any metric based on sessions like bounce rate, conversion rate etc . For this reason it is important you take action to mitigate Spam Referral within your Google Analytics.
EmbeddedAnalytics Referral Spam Alerts is a service which periodically scans referring links to your site and alerts you of any new spam referrers. While we don't have the ability to modify your Google Analytics to mitigate spam referrals (because the Analytics Export API is ReadOnly), you will at least be alerted and can take the proper action. We recommend following the steps in this document to modify your Analytics account to mitigate referral spam.Typical Referral Spam urls: