Peter Szor – a well-known security researcher, entrepreneur and author – has passed away, according to posts on Twitter.

“Another great researcher and dear friend has passed away. Peter Szor was a good friend, a researcher's researcher and a true gentleman,” Dave Marcus, McAfee director and chief architect, threat research and intelligence, wrote in a Twitter post.

In 1991, Szor earned his bachelor's degree from University of Veszprem in Hungary. He spent the next two decades developing and working on antivirus software, including Pasteur, F-PROT, AVP, Norton AntiVirus and McAfee, according to the biography on his website.

Szor wrote “The Art of Computer Virus Research and Defense,” which was published in 2005.