If the first wars were fought with sticks and stones, modern warfare is a high-tech battlefield where social media has emerged as a surprising — and effective — weapon. From Russian hacking to influence the American election to online recruitment for terror groups such as ISIS, an array of players are using false news and bogus accounts to stoke fear, incite violence and manipulate outcomes.

Authors Peter W. Singer and Emerson T. Brooking describe this as “likewar,” a term that plays on the Facebook “like” feature. In their new book, LikeWar: The Weaponization of Social Media, they explain how these platforms have become persuasive tools of propaganda. The recently joined the Knowledge@Wharton radio show on Sirius XM to discuss their work.

An edited transcript of the conversation follows.

Knowledge@Wharton: It is incredible how social media has developed and expanded rapidly in the last 20 years, and the impact it has had on politics.

Peter Singer: It’s absolutely fascinating. One of the people we interviewed for the book was the literal godfather of the internet itself, Vint Cerf. He talked about how it was once this military network for scientists, and then there was this moment when the scientists began to email back and forth about science fiction. That’s when he realized, “Hold it. It’s become this social thing.”

You move forward, and now [there’s] Facebook, Twitter, Instagram, you name it. They’re not just the nervous system of the modern world, they’re where we do business. They’re where we set up dates. But they’ve also become this space of battle, and battle over everything from political campaigns to use in military operations, marketing wars, you name it.

One of the things that the book is about is essentially how, if cyberwar was the hacking of networks that both governments and businesses have had to deal with, we now have this phenomenon of what we call “likewar,” which is the hacking of the people on the networks by this mix of “likes,” but also lies.

Knowledge@Wharton: You think about the stories we’ve heard about ISIS and other organizations using social media to recruit people. Can you talk about that?

Emerson Brooking: This issue came on our radar and the radar of a lot of folks across the country back in the summer of 2014, when the Islamic State invaded northern Iraq. They only had about 1,500 militants. They had pickup trucks and secondhand weapons from a lot of militant groups past.

But they did something new, and that was instead of keep their invasion a secret, they actually tweeted about it. They had a hashtag campaign, #AllEyesOnISIS, which they used to consolidate and broadcast their propaganda. And they had a huge network of both passionate supporters but also Twitter bots, which they used to lock down the trending hashtags on Twitter for the Arabic-speaking users.

“Over a very short period of time, a handful of tech geeks have become among the most powerful figures in all of politics and war.” –Peter Singer

As a result of that, even though they only had a small invading force, they were effectively able to spread fear [and seem to become] much greater than they were, and pushed these demoralized defenders of a city like Mosul — with 1.5 million residents — to drop their weapons and flee. In the process, ISIS started scoring these propaganda videos and weaving them back into their online messaging. It became a source of great inspiration for people following along at home.

It was a direct result of these online tactics that they were able to recruit some 30,000 fighters from the Middle East, but also the wider world — more than 100 countries where people would leave their homes to journey to Syria and Iraq to join them. Or if that wasn’t possible, they felt inspired to commit acts of violence at home.

Knowledge@Wharton: Is social media changing the military and defense strategy for some countries?

Singer: It has become a new battle space. To build on what Emerson was saying, it’s a battle space where a wide variety of actors with very different real-world goals are ending up using the very same tactics. You would see ISIS’ top recruiter, this hacker from Great Britain named Junaid Hussein, using the very same tactics that Taylor Swift uses to sell her music albums.

Or you would see in terms of organizational operations the approach that the Trump campaign used to win its online fight. It’s very similar to the model that Buzzfeed used to, in effect, rewrite the story of media.

Part of that aspect of it being a conflict is all the sides are watching, all the sides are learning. And they’re learning not just from whom they’re directly facing off against, but also from people in other kinds of conflicts. You see this proliferation of military campaigns to re-create these lessons. But then you also see private corporations starting to do the same. For example, Facebook talked recently about how it has created a “war room” to deal with these kinds of disinformation operations.

Knowledge@Wharton: Take us into that, because [CEO] Mark Zuckerberg has said that these problems are not something he would have conceived of when he developed Facebook in his dorm room at Harvard.

Singer: That’s one of the other just immense historic changes that we’ve seen: Over a very short period of time, a handful of tech geeks have become among the most powerful figures in all of politics and war. They don’t set out with this plan in mind. It’s a similar story not just at Facebook; it’s at Twitter. The very name Twitter is taken from a term for short bursts of inconsequential information, yet it’s shaping the outcome of elections, wars, you name it.

This handful of people are now making decisions on everything from what Russian disinformation campaigns are allowed to thrive or not, to should Myanmar’s generals be able to use their platform to call for genocide or not. It’s First Amendment questions that have hit everything from [conspiracy theorist] Alex Jones to activist groups.

“We’re all the targets of these wars. We’re the ones whose clicks decide whose side wins out.” –Peter Singer

In many ways, I liken it to parents going through the stages of grief at what has happened to their babies. First there was denial. For example, Zuckerberg famously says right after the election, it’s a “pretty crazy idea” that his platform could have been used in this way and could have shaped the way people voted. He’s saying that, though, at the very same moment that Facebook is marketing to political campaigns that this is the best space to influence people.

But you move forward a couple of years, and now he’s saying things like we are in an “arms race” against these adversaries. The tech companies have undertaken a series of activities that are certainly good, but they’ve clearly not gone far enough yet. And there’s a bit of bargaining going on with government of, “We’ll do this, but please stay out of our space.” I think that bargaining back and forth is really going to shape not only politics moving forward, but it will shape the internet for the rest of us.

Knowledge@Wharton: How is it also going to impact our culture in general?

Brooking: If you think that social media had a decisive impact in shaping the millennial generation, you need to look further. You need to look to the Gen Z folks who are growing up now, and the way a platform like Instagram is now the center of social life in these schools. It’s not a minor thing when you talk about something like bullying on Instagram, because it is the primary social gathering place after school.

But there are also more serious examples of how social media is affecting these folks coming up. In Chicago, some 80% of school fights now originate because of comments made online. Gangs recruit actively through these social media platforms. In the book, we tell the example of a very talented young rapper, Shaquon Thomas, who was also a proud member of a local gang, the Gangster Disciples. He winds up being the target of three hits by a rival gang. The first two times he gets away. Unfortunately, bystanders are killed in the process.

Typically, when you’ve survived something like that, you might lay low a while. But he immediately starts rapping about it because he sees it as great content and a great way to build his brand. Well, they get him the third time. He immediately becomes an online martyr. A week later, we see another shooting. This shooting happens because someone was making fun of Thomas, and it had originated because of a mean online comment. In gang violence generally, in crime moving forward, we see situations where a local argument that might start online can nonetheless spread or be answered by violence miles away or even in a gang franchise in another city.

“Something like a gang feud or even a really angry political argument, so much of it is performative.” –Emerson Brooking

When you think about it, something like a gang feud or even a really angry political argument, so much of it is performative. If you’re in one of these performative contests, it’s the logical tool to broadcast yourself to a wider audience. But the trouble is, just the way this information flows, we’re not yet really adapted to deal with it. Very quickly, emotions can make these feuds spiral out of control.

We draw on a lot of studies in the book regarding what’s called “emotional contagion.” It’s the rate at which emotions spread over social media, and how they influence people. Again and again, anger and outrage are shown to be the emotions that spread farthest and fastest, and incite others to violence.

Singer: Part of the research found that whatever the group, whatever the goal — whether it was private business, a political campaign, a gang, a celebrity — there were a series of new rules on driving your message viral, on winning the war of attention online. These helped explain why certain brands were thriving and other ones were losing.

One of the best businesses at this is Wendy’s. Another person that we interviewed for the book was a producer who was behind the Kardashians. But we also interviewed extremist group recruiters. It kept coming back again and again to these rules. One of them you talked about was emotion, and particularly the most powerful emotion, at least online, is anger.

It’s not just the case in our own politics. It plays out even in, for example, studies of the closed Chinese system. There are other key rules. There are things like narrative, there’s building online community, there’s inundation crossed with experimentation. What’s just utterly fascinating is these rules of the game are defining who is winning online.

But in a world where so much depends on winning online, it’s having very real-world effects. This is important to understand, whether you’re a business that’s dealing with these phenomena, but also all of us as individuals because we are the targets of these wars — whether it’s a marketing war or a real-world war. We’re the ones whose clicks decide whose side wins out.

Knowledge@Wharton: Is it as big a problem in Europe or Asia or Australia as it is in the United States?

Singer: It is, indeed, and it’s one that helps drive why these tactics are spreading. Let’s look at a micro-example: the use of bots, artificial voices online, to not just trick people as individuals, but also to drive overall internet trends, to steer things into your newsfeed and the like.

In the Brexit campaign, one-third of the online conversation was generated by these false voices. Of course, the online conversation is affecting not just the individual voter, but it also shapes what journalists are covering. They decide what to cover based on what’s trending. For example, the Mexican election was earlier this year. One-third of the online conversation was generated by bots.

We’re seeing this change the nature of politicians, but also CEOs that win out. Just like television created a demand to be telegenic and rewarded people who could do that, it’s the same phenomenon happening in social media. You’re seeing the rise of new types of politicians who are leveraging that, but also new types of CEOs. We could go back and forth on whether it’s for better or for worse, but just like TV, it’s having that same kind of effect.

Knowledge@Wharton: Can you talk about the role that social media has been playing for Donald Trump, both in his presidency and before?

Singer: That was one of the more fun but exhausting parts of the research. We went back and read all of Donald Trump’s old tweets, so you didn’t have to. The opening of the book is Donald Trump’s very first tweet, a little-known story where he is turning to social media to announce an upcoming TV appearance to try and save the ratings for “The Apprentice.”

He announces that he’s going to be reading the Top 10 List on Letterman, and it’s a way to market for the season finale of “The Apprentice,” which is sinking in the ratings. It’s this strange moment in time where you’re using social media to promote TV, and he, like the rest of us, begins to get addicted over time.

“In Chicago, some 80% of school fights now originate because of comments made online.” –Emerson Brooking

You can see over the next years, his style, his approach change. He also begins to hone some of the tactics that would take him into the presidency. For example, he begins online beefs. It’s a little bit of a parallel to what Emerson was talking about of gangsters. It’s this performative thing online, but it’s also to draw what he wants most, which is attention. Then his eye begins to turn to politics.

One of the other fun stories in this period is he announces the creation of a website as if it’s by a fan. It’s ShouldTrumpRun.com. He says, “Hey, everybody, what do you think about it?” What he does not reveal is that the website was created by Michael Cohen, his personal lawyer. But you move forward, and that very same account that was being used for business promotion, TV appearances, Trump Mattresses, etc., announces, “I’m honored to be the 45th president of the United States.” And we know it’s Donald Trump who wrote it because “honored” is misspelled.

Knowledge@Wharton: You used the word addiction, which is a recognition of the behavior in using social media. Tell us more.

Brooking: For many years, the designers of these social media platforms designed them to be addictive. Think about something as simple as the notification button, which is often a little red dot that you press on an icon to get rid of it and see who commented on you. Every part of that design is extremely deliberate.

Red is the color of a particular physiological arousal. You want to touch things that are red. Notifications don’t suggest what the notification is about. On Facebook, it could be an acquaintance’s birthday, but it could also be a long comment from a dear friend.

And for over a decade, there was no consideration whatsoever on the social impact of these platforms because it was thought that it was a universal good. The more people who were connected, the better. Now there is much more a reckoning regarding the social impact of these platforms, but there’s still a long way to go.

Knowledge@Wharton: What do you expect will happen?

Singer: There has been a pattern that goes back to the early days of MySpace and Six Degrees, Friendster, AOL — if you remember all of those. The pattern has essentially been that the platform companies have wanted to stay out of difficult political decisions of what’s on their network, but they’ve repeatedly been forced to intervene by a combination of their own customers getting angry and demanding it, and the fear of political intervention.

This goes back to the very first intervention in terms of policing internet porn, which appropriately enough came out of a fake news story. You’ll remember there was this claim that one-third of the internet was porn. It was actually drawn from a false story, but it had a real effect. This pattern has continued all the way to today, and you see the same thing playing out with Facebook and Twitter. That points to us as consumers, users, citizens of these digital empires who are going to demand it be cleaned up, and there’s a fear of government intervention that’s going to shape it.

There’s a second pattern, though, that concerns me. In trying to solve their problems, the technology companies always turn to new technology, and it then creates a whole new set of problems. You can see that, for example, with the newsfeed algorithm. And what looms is artificial intelligence.