Anti-secession demonstrators shout slogans and wave Spanish and Catalonia flags as they march in Barcelona on Nov. 18. (Manu Fernandez/AP)

On Oct. 1, the hashtag #Catalanreferendum took you to the world’s most popular conversation on Twitter. For more than 12 hours, Catalonia’s independence referendum became a trending topic worldwide. As would be expected, links, posts and articles from two Spanish media companies were the most virally distributed in the digital conversation. More surprisingly, the Russian media conglomerate formed by RT and Sputnik was the fourth most-used source, its content virally distributed as part of the digital debate.

How did RT and Sputnik manage to invade a digital conversation about a regional political crisis in Spain? Analysis of the 100 accounts that were most active in spreading the Russian media link reveals a disturbing figure: Eighty-four percent of those accounts are anonymous, and most of them appear to be controlled by digital bots.

Here’s how I did my research

To more accurately measure the digital conversation about Catalonia, we collected more than 5 million digital messages published from Sept. 29 to Oct. 5 that included the words “Cataluña” (Spanish), “Catalonia” (English) or “Catalunya” (Catalan). The majority were tweets, but we also collected Facebook posts, YouTube videos and items from other social media platforms such as Instagram, Blogger, WordPress, Reddit and Flickr.

We acquired these different data sets through the public APIs of those platforms, merged them into a single data set, and normalized and indexed it using big data software specializing in public sphere analytics.

RT and Sputnik were the fourth most virally distributed media group in the digital conversation

We found that, as you’d expect, traditional Spanish media was most active in the digital conversation about Catalonia. The Catalonian newspaper “La Vanguardia” ranked first, with 5,095 articles published.

The website whose content, articles and social media posts were most highly distributed was eldiario.es, an online news outlet founded in September 2012. The website’s 72,488 shared posts may have reached up to 136.9 million individual readers. Next came the British BBC, whose 70,457 shared posts reached a potential maximum audience of 218.2 million, and the Spanish newspaper, El País, whose 52,042 shared posts had a potential maximum audience of 208.1 million.

Here’s what’s stunning: RT News and Sputnik appear in fourth position. Together they distributed 47,964 Catalonia-related posts that reached up to 125.9 readers or viewers. The contents published by Sputnik and RT were shared 10 times as widely as that those published by the Spanish public television RTVE or the Spanish public news agency Agencia EFE.

What did RT and Sputnik have to say about Catalonia?

We did a qualitative analysis of RT’s 10 most-shared links and social media posts related to Catalonia, and found RT had a special interest in sharing images and videos of people injured during clashes with the police. Fully 50 percent of its 10 most-shared posts and links denounced the actions of the Spanish police. Another 20 percent highlighted how much Catalonian independence would hurt the Spanish economy; 20 percent offered an apparently neutral approach; and 10 percent criticized and politically attacked Spanish Prime Minister Mariano Rajoy.

Meanwhile, the Sputnik group’s 10 most-shared posts about Catalonia all favored the Catalan independence groups’ narrative. Of these, 40 percent denounced Spanish police actions; 30 percent criticized the Spanish prime minister; and 30 percent noted international support for Catalonia’s independence.

Who was sharing these RT and Sputnik posts?

So who was spreading all this “news”? To find out, we analyzed the 100 social network accounts most active in sharing RT and Sputnik’s posts about Catalonia from Sept. 29 to Oct. 19.

Here’s what we found. Only nine of the 100 most active accounts seem to follow human behavior in their publishing and interaction strategies. Seven other accounts correspond to official profiles on social networks of RT and Sputnik. The remaining 84 accounts cannot be identified with any real person or institution; do not generate any original content or posts; and propagate others’ links and social media posts in a constant, systematic and massive way, in most cases using RT and Sputnik as their main source.

All of that strongly indicates that 84 percent of the key accounts that systematically and broadly disseminated RT and Sputnik’s Catalonia content are most likely digital bots. Some of them, like @bobbit2266, @rickrick888 or @ivan226622 post the same content at the same time, and others like @domz97819744 post an average of 1425 messages per day.

We can divide this network of anonymous digital profiles into three groups. The first group, with 24 percent of these accounts, clearly shows sympathy toward the Nicolás Maduro and Hugo Chávez regime in Venezuela.

A second group, with 37.7 percent of the accounts, are almost exclusively devoted to redistributing or retweeting RT and Sputnik content. Unlike the accounts related to the “chavista” movement, this second group hides under well-elaborated covert identities. In some cases, these accounts publish the same content at the same time, reinforcing the hypothesis that they are digital bots enacting a coordinated strategy.

The third group of 27.3 percent massively distributes and retweets content published by various international media outlets, not only RT and Sputnik. In the last week, Twitter removed 7.1 percent of the most active accounts.

These findings raise many questions. Who or what is behind this troop of digital zombies? Why do Russian media and Venezuelan digital profiles pay so much attention to spreading news of an institutional crisis within a European Union democracy? What interests drive their editorial strategies? Are those behind these actions also investing in less visible paid advertising campaigns? Has this anonymous army been involved in other digital battles in Europe or the United States? Are these zombies influencing major governance and institutional crises around the world?

Javier Lesaca is a visiting researcher at the School of Media and Public Affairs at George Washington University. Find him on Twitter @lesacajavier.