List of domains used to spam in Google Analytics:
topseoservices.co
video--production.com
fast-wordpress-start.com
googleweblight.com
lastpass.com
*.inspsearch.com
alibestsale.com
floating-share-buttons.com
get-free-social-traffic.com
hosting-tracker.com
*.free-floating-buttons.com
boost-my-site.com
black-friday.ga
quit-smoking.ga
kadima-zoran.muni.il
get-your-social-buttons.info
website-analyzer.info
traffic2cash.org
*.copyrightclaims.org
santasgift.ml
alert.scansafe.net
ranksonic.net
traffic2cash.net
*.2your.site
*.snip.to
*.snip.tw
*.for-your.website
lsex.xyz
rusexy.xyz
trafficgenius.xyz
traffic2cash.xyz
They are using botnets to send traffic and change Google Analytics statistics so you don't know if you are looking at real traffic.