At the University of Pennsylvania last fall, someone splattered red paint on a statue honoring Benjamin Franklin, the school’s founder.

Within hours, campus workers washed it off. But the university was eager to find the culprit.

A pro-Palestinian group had claimed responsibility on social media. The university examined footage and identified a student’s cellphone number using data from the campus Wi-Fi near the statue at the time it was vandalized. Campus police obtained a search warrant…