Good question - There are few ways to determine if you’re a victim of click fraud:
Your conversions decreased drastically while your clicks / budget remains the same.
You've noticed an unusually high number of clicks in your Google Ads dashboard.
You are in a competitive industry (locksmith, lawyers, doctors etc).
You suspect your competitors are clicking on your ads.
You suspect one of your unsatisfied customers may be seeking revenge.
You are running campaigns on the Google Display Network without vetting the sites that are displaying your ads.
Annoyingly, sometimes things can still look normal in your Google Ads account even if you are suffering from click fraud.
To be sure that you’re stopping click fraud, ensure that your ads are protected.