Jim Jones@silverwizard here is a Forbes article (that also points to more sources) on how to do it. Beware that it isn't a quick fix, but it can work if they are persistent (and it require some legal action, which isn't always affordable). https://www.forbes.com/sites/kashmirhill/2012/09/28/how-to-bait-and-catch-the-anonymous-person-harassing-you-on-the-internet/
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