This is the correct answer. You may be able to filter data to some extent in the dashboard using special views, but if you want a 100% guarantee that your data stays reliable, currently your best bet is not to use GA, or at least complement it with another tool.
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You can't know. GA spam is rampant, more so via referer spam than anything else.
This is the correct answer. You may be able to filter data to some extent in the dashboard using special views, but if you want a 100% guarantee that your data stays reliable, currently your best bet is not to use GA, or at least complement it with another tool.
Referrer spam is the worst. This was on a reddit thread today: https://i.imgur.com/mRGiiBQ.png
note the: how to stop referral spam url