How do you tell a vandal from a visitor? Art museums are struggling

FOR Hans-Peter Wipplinger, the director of Vienna’s Leopold Museum, November has been challenging.

As climate protesters across Europe stepped up their attacks against art, Wipplinger took measures to protect his storied collection, which includes famous paintings by Gustav Klimt and Egon Schiele. Bags were banned; coats, too. The museum hired extra guards to patrol its five floors.

It didn’t work. Last week, members of a group called Last Generation walked into the museum and threw black liquid at one of Klimt’s major works, Death and Life. A protester had sneaked the liquid into the museum in a hot water bottle strapped to his chest, Wipplinger said.