On 19 July 2024, millions of Windows computers around the world crashed and would not restart normally. Airlines grounded flights, banks and shops struggled to take payments, and some hospitals disrupted services. The cause was a faulty content update from the cybersecurity company CrowdStrike, sent to computers running its security software. It was not an attack, but a mistake in an update.
Why one update could do so much
Security software runs deep inside the system, with a high level of access, so a fault there can stop the whole computer. The update reached very many machines very quickly. Fixing it often needed someone to restart each computer manually.
Lessons for any organisation
- Test before you release. Updates should reach a few machines first.
- Plan for failure. Keep paper or offline backups for critical tasks and know who to call.
- Back up your data and check that you can restore it.
- Do not depend on one thing. Single points of failure hurt everyone at once.
A lesson for learners
Even professionals make mistakes, and small errors in code can have large effects. That is why testing, careful review and calm problem solving are core parts of programming, and why we teach them from the first lessons.