Rachel Gross was midway through her presentation at a Jewish Community Library event on Sunday, talking about the Jewish cultural history of Crisco. There were close to 200 attendees at the event held on Zoom, the popular videoconferencing app that has become a mainstay of online life during the pandemic.

But not everybody was there with good intentions.

“About halfway through the lecture, I was sharing my screen and somebody started scribbling on it,” said Gross, an assistant professor at San Francisco State University. She wasn’t even sure it was malicious at first. “It took me a minute to find out what was going on,” she said.

The scribbling was the first sally in a “Zoombombing” of the event, with several people yelling out vulgar language and drawing what looked like genitalia and possibly a Star of David on the screen, visible to all.

The disruptors were removed by the moderators, but after a brief pause, others barged in, even addressing Gross by name.

“It turns out, having people say crude things to you by name is pretty upsetting,” said Gross, who teaches in the Jewish studies department at SFSU.

Library director Howard Freedman said the organization had taken recommended security steps for the lecture, including requiring attendees to register with email addresses — information that the Zoombombers themselves provided.

“One of them said as much yesterday,” Freedman said. “’Yeah, now thousands of people have this [link].’” (The link was only for one lecture, not the entire library series.)

The disruption was only momentary. When the trolls attempted to take over the presentation, Freeman and Jewish LearningWorks director David Waksberg removed the troublemakers as quickly as possible.

“They were so, so great,” Gross said. “I was so appreciative.”

She was able to continue her talk undisrupted, although of course everyone was unsettled.

“People said the talk was good, but, yeah, I felt a little rattled by it,” she said.

“Rachel proceeded with such grace,” Freedman said. “I think none of us wanted these people to win.”

The issue going forward, he said, is in figuring out how to continue offering events that are accessible to the community while keeping trolls and Zoombombers out. For public events that are online, there is no way to know whether every attendee is there for legitimate reasons.

“It’s very difficult to vet people, and laborious,” Freedman said.

The organization is regrouping to consider how to tackle the problem.

“For me this was a really valuable learning experience, and it’s going to be the start of a soul-searching process for us,” Freedman said.