In January, WhatsApp limited how often messages can be forwarded—to only five groups instead of 20—in an attempt to slow the spread of disinformation. (They had previously limited it to 20 from 256.) New research suggests that the change is working, but more can still be done.

The background: When it comes to disinformation, Facebook and Twitter receive most of the attention. But WhatsApp has influenced elections in Brazil and India, and a recent report from NYU highlighted it as one of the platforms we should be worrying about more.

Measuring disinformation on WhatsApp can be tricky. Unlike Facebook and Twitter, WhatsApp is a private, encrypted chat tool, which means a lot of content is out of reach. It can be hard to figure out whether new changes, like the forwarding limit, are really working. “I’m from India, and during the recent election, people were saying that the forwarding limit wasn’t helping much,” says Kiran Garimella, a MIT postdoc and coauthor of the preprint. But that was based on anecdotes.

How to study WhatsApp: Of course, Garimella and his colleagues couldn’t access private chats. But there are enormous public groups that people can join, and political candidates are increasingly using these groups to contact voters. So the researchers joined thousands of these public groups in Brazil, India, and Indonesia. By scraping the data and analyzing nearly six million public messages across three countries, they were able to rebuild a network and run simulations to test how different forwarding limits affected how quickly information with different levels of virality could spread.

The results: They found that changing the forwarding limit to five slowed down the spread of information by roughly an order of magnitude. Under the new limit, 80% of messages died within two days, but 20% were still very viral and reached the full network during this time, according to Garimella. The result isn’t perfect because, again, it only uses public data, but it shows what seemingly small fixes can do.

The researchers suggest that WhatsApp could be more effective by taking a hands-on “quarantine” approach and directly limiting forwarding on specific messages or from specific people. “They know if a piece of information is viral,” says Garimella, and fact-checkers could see if the information is true. “They know who has started it and has shared it, so you can put a limit on bad users or information,” he says.

What does WhatsApp say?: According to a company spokesperson, the forwarding limit has diminished the total number of forwarded messages on WhatsApp by 25%. The company has created new labels to tell users when they receive a chain message and launched a fact-checking service in India.

Correction: An earlier version of the story said that WhatsApp limited message forwarding to five groups from 256 in January. It limited forwarding to five from 20. The platform had previously limited the amount to 20 from 256.