A lot of entrepreneurs have “a moment”. A moment that makes them realise they’re on to something.

start-up company Malwarebytes was less than a year old back in late 2008, but already gaining a good reputation in the cyber security world.

For Marcin Kleczynski it came while he was discreetly working on his antivirus software business from his student digs.

His start-up company Malwarebytes was less than a year old back in late 2008, but already gaining a good reputation in the cyber security world.

Marcin, then only 18, was just about managing to juggle running his start-up with participating in student life at the University of Illinois when he hit a snag.

“I was having some real trouble analysing the latest computer virus, when all of a sudden I get a white page on my screen that says ‘you’ve been banned from the school network due to malicious activity on your desktop’,” he says.

“They’d obviously detected that I had a virus on my computer, but didn’t realise it was deliberate. So I call the university IT helpline, and they send a kid, no older than me. He sits down at my computer and looks at it and says ‘boy you’ve really screwed this thing up’.

“Then, right in front of me, he logs onto my website and downloads Malwarebytes. I didn’t say anything, I stood behind him and watched him fix my computer with my software to get me back online. He left never knowing who I was, but to this day I love that moment.”

By the time Marcin graduated with a degree in computer science in 2012, he had quietly grown Malwarebytes into a business earning a few million dollars a year. All without any of his lecturers having any idea what was taking up his time, and pushing his grades down.

Today the company has an annual turnover of more than $126m, and millions of customers around the world.

Born in Poland in 1989, Marcin moved to the US with his family when he was three, settling in Chicago.

As a gaming-obsessed teenager, he’d accidentally got a virus when he was 14, and learned everything he needed to know about computer bugs from internet forums and a “For Dummies” book.

Formally launching Malwarebytes in January 2008 when he was just 18, it grew quickly, and he decided that starting university in September of that year would just slow him down. His mother had other thoughts.

“The business was becoming real, and so I went sheepishly to my mum and said ‘I don’t think I’m going to go to school’,” says Marcin. “Fifteen seconds later we were packing my stuff and I was going to school.”