Definitive Guide to Removing All Google Analytics Spam http://help.analyticsedge.com/spam-filter/definitive-guide-to-removing-google-analytics-spam/

http://help.analyticsedge.com/spam-filter/definitive-guide-to-removing-google-analytics-spam/

Google analytics shows traffic from sharebutton.to

compliance-alexa.xyz

The most effective solution is a valid hostname filter as described by StevieD_Web, but note that there are also some crawlers that get past this defense, so you would also need additional filters to get a clean report.