It's the era of the side hustle, and if you've ever considered starting one to earn some extra cash outside of your 9-5, you're in good company. These days, more than one-third of U.S. adults have side hustles, and their supplemental gigs make an average of $891 a month, according to recent research from Bankrate. Of course, the most successful side-hustlers see much higher earnings, especially when they start a business that brings in nearly as much as — or significantly more than — their full-time sources of income.

Marcin Kleczynski, 35, is a Bay Area-based entrepreneur who was a teenager when he "unofficially" started the side hustle that would become a cybersecurity firm. Now the CEO, he and his co-founder Bruce Harrison have grown the venture into a multi-hundred-million-dollar business. Responses have been edited for length and clarity.

Image Credit: Courtesy of Malwarebytes. Marcin Kleczynski.

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What was your day job or primary occupation when you started your side hustle?
Before heading off to college, I worked at a local break-fix computer shop called Computer Express. It was a small, scrappy place, but it gave me invaluable hands-on experience fixing all kinds of machines. I got to see firsthand how often people were struggling with malware and tech problems, and that experience stuck with me. It's where the idea for Malwarebytes for me was planted and started to take shape.

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