As a teenager, Kleczynski found a job working as a technician in a computer repair shop in Chicago.[1] It was while working at the repair shop in Chicago that Kleczynski noticed that whenever infected computers arrived, they would generally reformat the computer, regardless if the infection was only minor. It was only when his mother's computer became infected that Kleczynski learned more about why the virus wasn't directly attacked, finding that neither McAfee nor Symantec would remove the malware from his system.[2] He later recalled "I've never been as angry as when I got my computer infected", and professed that his mother told him to fix it "under penalty of death".[3] It was only after Kleczynski posted on the forum SpywareInfo, popular at the time, that he was able to learn how to cure it, which took three days. The company was unofficially founded after this, when Kleczynski conversed and became friends with several of the editors of the forum, who tempted him to buy an unused domain from them.[2] As a result, Malwarebytes was informally established in 2004.[4]
Kleczynski began writing his own free software tools in Visual Basic.[5] With one of the site's regulars, Bruce Harrison, Kleczynski wrote the inaugural version of the company's software.[3] In 2006, worked with a college roommate to produce a freely available program called "RogueRemover", a utility which specialized in fighting against a type of infection known as "rogues", which scam computer users into giving away their credit card information through fake anti-virus software. RogueRemover proved instrumental in developing Malwarebytes Anti-Malware, and Kleczynski was able to set up a forum which enabled him to improve the software through feedback.[2] Kleczynski and Harrison formally launched Malwarebytes on January 21, 2008 while Kleczynski was studying computer science at the University of Illinois.[2][3] Bruce became the VP of Research for Malwarebytes and he further hired Doug Swanson, an experienced freeware development technician.[2] Kleczynski and Harrison reportedly made $600,000 in their first year of selling the software, despite not having met personally at the time.[6] Kleczynski reportedly made his first million by the time he was 19.[7]
In 2014, Malwarebytes received $30 million in funding from Highland Capital, and by the following year it announced that it had treated 250 million computers worldwide, representing about 20-25% of working business computers.[6] In June 2015, Kleczynski moved the firm's headquarters from 10 Almaden Boulevard in San Jose, California to a new 52,000 square feet (4,800 m2) office space on the two top floors of the 12-story 3979 Freedom Circle in Santa Clara, California. The new office is more than twice the size of the former office. The company reported a growth of 10 million users in just one year, from 25 to 35 million active users at the time, and an increase in revenue by 1653 % in 2014.[3] In January 2016, Malwarebytes unveiled advanced anti-ransomware package Endpoint Security,[8] and announced that it had raised $50 million in investment from Fidelity Management and Research Company.[9]
Working with the Malwarebytes team, Kleczynski has delivered several popular products in the Internet security field, including Malwarebytes Anti-Malware, which offers "real-time protection against malware, automated scanning, and automatic updating".[10] Malwarebytes Anti-Malware Mobile, a free Android app which protects smartphones,[11] Malwarebytes Anti-Exploit, which protects vulnerable programs from attack,[4][12] and Malwarebytes Endpoint Security, an advanced anti-ransomware package.[8][13] Kleczynski cited the reason for launching the anti-ransomware technology in 2016: "In the last six to 12 months, this has just gone so aggressively to the business environment. We see companies from 25 people all the way to 250,000 people getting hit with ransomware".[14]