Daniel Kaminsky, a security researcher known for his discovery of a fundamental flaw in the fabric of the internet, died on Friday at his home in San Francisco. He was 42.
His aunt, Dr. Toby Maurer, said the cause was diabetic ketoacidosis, a condition that led to frequent hospitalizations in recent years.
In 2008, Mr. Kaminsky was widely hailed as a digital Paul Revere after he found a serious flaw in the internet's basic plumbing that could allow skilled coders to take over websites, siphon off bank credentials or even shut down the internet. Mr. Kaminsky alerted the Department of Homeland Security, executives at Microsoft and Cisco, and other internet security experts to the problem and helped spearhead a patch.