Prevx's technology will be integrated into Webroot's cloud security services portfolio as part of the deal, which the latter said will "transform how security is delivered."
Financial details of the purchase remained undisclosed at the time of publishing.
"Webroot and Prevx share a common vision for revolutionising what we believe is a market in need of dramatic change," said Dick Williams, chief executive (CEO) at Webroot.
"This technology, combined with Webroot's innovations, customer service and support, will make it easy for consumers to stay protected online wherever they go and easy for businesses to protect their employees and their networks."
Williams promised the companies would provide the "best security service in the world" and described the acquisition as "a seminal event" for the industry.
Prevx founder Mel Morris said the two firms had a common "desire to innovate" during a time when the industry had fallen behind in the fight against cyber crime.
"Today's cyber crime industry is rife with zero day exploits, social engineering and sophisticated techniques which make it possible for threats to get past traditional malware detection," Morris added.
"We are pleased to become a part of Webroot and join forces in leading a revolution in the security industry."
The announcement comes on the back of a number of recent acquisitions by Webroot, including those of email security provider Email Systems and website classification company BrightCloud.
Elsewhere in the security industry, there have been some major buys this year, including Intel's $7.68 billion acquisition of McAfee.
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Tom Brewster is currently an associate editor at Forbes and an award-winning journalist who covers cyber security, surveillance, and privacy. Starting his career at ITPro as a staff writer and working up to a senior staff writer role, Tom has been covering the tech industry for more than ten years and is considered one of the leading journalists in his specialism.
He is a proud alum of the University of Sheffield where he secured an undergraduate degree in English Literature before undertaking a certification from General Assembly in web development.