This was the subject of a fascinating talk delivered by Tamar Mitts, an assistant professor of international and public affairs at Columbia University, at a “data science day” hosted by the school on Wednesday. Mitts studied the efficacy of Twitter-disseminated propaganda supporting the self-identified Islamic State, or ISIS, in 2015 and 2016. To avoid the “obvious ethical issues” which attend to subjecting humans analysts to ISIS propaganda, Mitts said she used machine learning algorithms to identify and sort messages and videos into various categories, such as whether they contained violence. Then she parsed her dataset to uncover trends.

Mitts’ results were a revelation. Even though people tend to associate ISIS propaganda with heinous acts of brutality—beheadings, murder, and the like—Mitts found that such violence was, more often than not, counterproductive to the group’s aims. “The most interesting and unexpected result was that when these messages were being coupled with extreme, violent imagery, these videos became ineffective,” Mitts said. In other words, the savagery for which ISIS became famous did not appeal to the majority of its followers; positive messaging found greater success.

There’s a caveat though: Anyone who was already extremely supportive of ISIS became even more fanatical after encountering a piece of propaganda featuring violence. So, while violent acts turned off newcomers and casual sympathizers, they nudged ideologues further down the path of radicalization. Extremism begets polarity.

In the wake of the Christchurch massacre, Mitts’ research gains even more relevance. Tech giants are continuing to fail to curb a scourge of violence and hate speech proliferating on their sites. World governments are, meanwhile, passing ham-fisted policies to stem the spread of such bile.

Perhaps Mitts’ discoveries could help society to avoid repeating history’s darkest moments. My appreciation for her work grew after I finished reading In the Garden of Beasts, a gripping journalistic endeavor by Erik Larson, which details the rise of Nazi Germany through the eyes of an American ambassador and his family living in Berlin. Afterward, I watched a YouTube video—an innocuous one—recommended by the author: Symphony of a Great City, a 1927 film that documented the daily life of ordinary Berliners at that time. It amazes me to think how, within a few years, these souls would come under the sway of Hitler’s bloodthirsty regime.

While the Internet makes zealotry easier than ever to incite, today’s tools also make it easier to study.

Robert Hackett

@rhhackett

robert.hackett@fortune.com

Welcome to the Cyber Saturday edition of Data Sheet, Fortune’s daily tech newsletter. Fortune reporter Robert Hackett here. You may reach Robert Hackett via Twitter, Cryptocat, Jabber (see OTR fingerprint on my about.me), PGP encrypted email (see public key on my Keybase.io), Wickr, Signal, or however you (securely) prefer. Feedback welcome.

THREATS

Marred-a-Lago. The U.S. Secret Service apprehended a suspicious Chinese woman who attempted to enter President Donald Trump's Mar-a-Lago resort in Palm Beach, Florida. The woman, Yujing Zhang, was carrying four cellphones and a thumb drive infected with malware. One of the stories she spun: She said she was there to use the pool, though she had no swimsuit.

Verboten. German chemical giant Bayer said it contained a cyberespionage intrusion by suspected Chinese hackers. The company discovered the computer infection early last year and then quietly analyzed and monitored the intruders before booting them from the network last month. "There is no evidence of data theft," the company said.

Thrill of the chase. Jamie Dimon, CEO of JPMorgan Chase, highlighted the importance of digital security in his annual letter to shareholders this week. "The threat of cyber security may very well be the biggest threat to the U.S. financial system," he wrote. "[T]he financial system is interconnected, and adversaries are smart and relentless – so we must continue to be vigilant."

Show me the money. The city of Albany, New York, and iced tea-maker Arizona Beverages were recently hit with ransomware attacks. Norsk Hydro published a video featuring interviews with employees who grappled with a recent plant-crippling ransomware attack. And the Federal Bureau of Investigation said it had to change the way it conducted cyberattack investigations after wrestling with the SamSam ransomware campaign, which affected cities such as Atlanta and Newark.

Bezos vs. Saudis. Gavin De Becker, the investigator hired by Amazon CEO Jeff Bezos to find out who obtained private text messages and photos relating to his extramarital affair, said he has concluded that "the Saudis had access to Bezos' phone, and gained private information." A spokesperson for Saudi Arabia told CNN that the kingdom "categorically rejects all allegations that it is involved in any fashion in the apparent dispute."

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ACCESS GRANTED

Creepy crawlers. Meet Eva Galperin, a hacker-activist who studies commercial surveillance software, so-called stalkerware, as head of the Electronic Frontier Foundation's threat lab. Now Galperin is calling on Apple and antivirus companies to protect people from these privacy-infringing tools, as Wired's Andy Greenberg writes. More extremely, Galperin is asking government officials to prosecute executives at companies that sell this kind of software.

Over the last year, Eva Galperin says she's learned the signs: the survivors of domestic abuse who come to her describing how their tormentors seem to know everyone they've called, texted, and even what they discussed in their most private conversations. How their abusers seem to know where they've been and sometimes even turn up at those locations to menace them. How they flaunt photos mysteriously obtained from the victim's phone, sometimes using them for harassment or blackmail. And how none of the usual remedies to suspected hacking—changing passwords, setting up two-factor authentication—seem to help.

The reason those fixes don't work, in these cases, is because the abuser has deeply compromised the victim's phone itself. The stalker doesn't have to be a skilled hacker; they just need easily accessible consumer spyware and an opportunity to install it on their target's device. An entire industry of that so-called spouseware, or stalkerware, has grown in recent years, one that Galperin argues represents a deeply underestimated scourge of digital privacy.

FORTUNE RECON

A British Spy Agency's London HQ Operated in Secret for 66 Years. Turns Out, It Was Right Next Door. by Phil Boucher

Domestic Terrorism Is on the Rise. But How Prepared Is the U.S. to Counter It? by Natasha Bach

Proposed Law Would Require YouTube and Netflix to Do More to Protect Kids Online by Danielle Abril

If the Full Mueller Report Is Released, Here's What You'll Actually See by Renae Reints

Who Should Own Your Health Data? by Erika Fry

Mark Zuckerberg Has Made the Case Against a Fragmented Internet. Here's the Case for It. by David Mayer

How True Crime Podcast 'The Murder Squad' Will Crowdsource Investigations by Dan Reilly

ONE MORE THING

Xinjiang jail. In this chilling multimedia piece, The New York Times takes viewers inside Kashgar, a Chinese city that the Communist Party has effectively transformed into a gigantic prison. Residents are required to keep software on their phones that monitors calls and messages. They are forced to stop at checkpoints to have their faces and ID cards scanned. Surveillance cameras are ubiquitous and neighborhood watches grade people based on their "reliability." As the Times writes, this dystopia is "as much about intimidation as monitoring."