Half a Second
The Backdoor That Almost Broke the Internet, and the Invisible Labor Beneath It
Welcome
On March 29, 2024, a Microsoft engineer running a routine benchmark at home noticed that logging into a test machine was taking about half a second longer than it should. Almost anyone would have written it off as noise. He chased it instead, and found a backdoor: a hidden, deliberately built way into XZ Utils, a small compression tool that sits unnoticed on nearly every Linux system on Earth, including the servers that carry much of the traffic of the internet. Someone had spent two years putting it there.
Half a Second tells that story as one continuous narrative: the burned-out volunteer who maintained the code alone and was patiently, expertly manipulated into giving it up; the engineer whose half-second of curiosity caught the attack through a chain of luck and hard-won instinct; and the operator who built it, who has never been identified and, this book argues, may never be.
The catch is where the book begins, not what it is about. Underneath the story is a quieter, structural fact. Much of the world’s digital infrastructure is in fact well supported: large companies pay the engineers who write most of the Linux kernel, and the open-source commons draws real and growing investment. But the same economy that funds the big, visible pieces leaves many of the small, unglamorous ones that everything also depends on to a handful of volunteers, often unpaid and overstretched. XZ Utils, maintained for years by a single exhausted person, was exactly that kind of piece, and the incident is the moment that imbalance briefly came into view.
This is interpretive narrative nonfiction, written for the general reader. It assumes no technical background: everything it needs is explained in plain language, in the order the story reaches it.
This is the web edition of Half a Second. Use the sidebar to navigate the parts and chapters. You can also download the PDF edition.
License
Copyright © 2026 Adrian Mastronardi
This website is and will always be free, licensed under the CC BY-NC-ND 4.0. If you appreciate reading the book for free and would like to give back, please consider donating to the Open Source Collective, which funds the open-source maintainers this book is about.