The Hacker Who Chose Defense

In a culture that often treats "hacker" as a dirty word, one security leader wants to reclaim it. Rob Juncker, chief product and technology officer at Mimecast, is unequivocal about his own past: he was a hacker, and he believes that is a strength, not a liability. His story—from a curious ten-year-old dismantling his family's first computer to a social engineering caper that fooled a phone company—offers a rare window into how a teenage troublemaker became a senior defender of corporate networks.

An Apple IIc and a Calling

Juncker's path began when his parents brought home an Apple IIc for word processing. He was 10. Within two days, the machine was in pieces on the floor as he tried to understand how it worked. The curiosity, a thirst for knowledge, predated the computer, but the arrival of the Apple focused it sharply.

Learning resources were scarce for a child in that era, and formal training was nonexistent. He figured out that software made the machine act, so he taught himself Basic by reading the code on screen and experimenting with commands. "Pretty soon I found myself sitting there with the command prompt and starting to program in Basic," he recalled. "I think that was my first experience of the beauty of computers and electronics in general. Suddenly I was unlocking a world where I could write something and create it. It was like an artist being given a paintbrush for the first time and then realizing that you don't need to stick within the confines of what's on the paper in front of you – rather, you create your own canvas and what you can do with it."

That artistic analogy would recur throughout his life. From the start, he saw hacking not as mere mischief but as a form of creation—and the computer as a canvas with infinite potential.

Modems, Wardialers, and a Forged Letter

Then came modems, operating at a then-standard 300 baud. To a teenager, the ability to connect to distant systems was pure magic. His parents had a modem, but he wanted more. He discovered wardialers and realized a dedicated phone line was necessary to fully explore. His parents refused.

So he took matters into his own hands. "I did what any hacker would do," he says. He called the phone company and ordered a line. The best part, as he tells it, came before the installation appointment. He ran laps in the basement to raise his body temperature, faked being sick so he could stay home from school, and when the engineer arrived, he was alone—armed with a forged letter from his father.

The forgery was simple. The family's computer served as a word processor, and the engineer had no reference signature. The letter claimed the family wanted a dedicated low-noise line for a modem. It worked. In that moment, Juncker added social engineering to his skill set—all because he wanted access to games he couldn't afford. "I effectively did the first 'deepfake': a kid faking his father and ordering a phone line," he says. "I had no legal right to do this, but I succeeded in doing it."

With the new line came more serious activities. He admits to downloading early pirated software, which eventually landed him in trouble. But the real reckoning came with a knock at the door in his early teens.

The Knock That Changed Everything

"One day a certain US legal organization came to the house and the doorbell rang," Juncker recalls. His mother answered. He overheard the visitor say, "We need to have a conversation with you all. We understand that there has potentially been some activity here relative to tapping into phone lines or trying to gain access to certain services." It was true. He had been trying, though he hadn't succeeded.

His mother initially denied it, but then realization struck. He heard her call his name. They sat down and had the conversation. The outcome: he lost his second phone line and had to rein in his activities. He received a warning. "Long story short, I lost my second phone line and had to rein back on my activities. I received a warning," he says. "And I'm grateful that I got a warning at that point, because had I continued along the path I was on, I think I would have ended up with more than just a warning. It was a turning point for me."

The threat of jail time flipped a switch. He realized he needed to change course. But the warning alone might not have been enough without a second influence: economics.

Economics and the Artist's Canvas

In college, Juncker combined computer science with economics. "If you mix Computer Science and Economics, you actually get the most boring geek on the face of the earth," he jokes. But the combination was transformative. It showed him that computer skills could be used for legitimate, well-paid work—protecting systems rather than attacking them.

"What I learned through economics is you can make really good money in software and do great things with computing," he says. "I'll go back to that artist analogy. I believe that hackers and their curiosity are no different than artists. The artist in the hacker doesn't simply wish to paint a new picture; he wishes to create a new canvas on which to paint."

He excelled on that new canvas, pushing boundaries through curiosity. He often challenges the status quo, citing a favorite quote from computing pioneer Grace Hopper: "The most dangerous phrase in the language is, 'We've always done it this way'."

A Moral Compass Emerges

In his early twenties, a third factor emerged: health issues. They forced him to confront deeper questions. "As I went through those health problems, I asked myself, 'What defines me; what is the legacy I want to leave in this world?'" The answer, simple to state but hard to live: "I really want to leave the world a better place."

That answer crystallized a moral compass that had perhaps always been there, subtly keeping him on the right side of the law when he was younger. Now he became fully aware of it. Morality became his North Star. "That North Star brought me to a place where I can use everything I've learned and the skills I've acquired to defend organizations – to make the world a little safer," he says.

His intimate knowledge of how to attack systems gave him unique insight into how to defend them. He has spent his professional career doing exactly that, with senior R&D and engineering roles at VMware, LANDesk, and Ivanti before joining Code42 in 2017. He became Code42's CTO in 2020, and moved to Mimecast when it acquired the company in July 2024.

Defending with an Attacker's Mindset

Today, as chief product and technology officer at Mimecast, Juncker combines everything he began learning at age 10: software, technology, and security. His journey from wardialing to boardroom illustrates how early curiosity, when channeled constructively, can become a powerful force for defense. He believes every security leader should be able to answer "yes" to the question of whether they are a hacker—because understanding the attacker's perspective is essential to building effective protections.

In an industry where terms like "hacker" often carry stigma, Juncker's story is a reminder that the same skills and mindset can be used to break or to build. For him, the choice came down to a moral compass—and a warning that arrived just in time.