My housemate is a software developer. Please understand that this is paraphrased and any errors are my own, not his. But here's a basic explanation:
Crowdstrike is a cybersecurity company in the US. They have a program for large-scale business networks called Falcon, that detects malicious activity on large networks. Loads and loads of businesses use this. Crowdstrike pushed an automatic update to Falcon today.
The way I understood my housemate, the update installs a driver on your computer. When it kicks in, it accidentally causes a Directed Denial of Service, or a DDoS, on your system. This means it overloads the system with requests for info, causing it to crash.
The only way to get rid of it is to physically go to the affected computer, boot it in safe mode, and delete the file so that Falcon stops working and lets the computer start up without DDoSing it. If a computer can't boot up in safe mode, it can't turn back on at all, and therefore can't be fixed.
Let me put that another way: This can't be fixed by Crowdstrike pushing out an automatic update. It needs people to physically access their machines.
So what does that mean? Well for starters, my housemate thinks it's possible that every single virtual machine which has installed this update is bricked. Utterly bricked. Cause VMs can't typically boot into safe modes. And even computers that are stored offsite to their owners? Bricked til they're accessed. This can't be done en masse via remote access methods like SSH, just as it can't be done by pushing out an auto-update. The computers can't turn on normally.
And the vast majority of web services are run either on remote servers or virtual machines.
This will likely spark some massive changes to computer infrastructure safety. Cause on affected systems, doctors can't access patient records, airlines can't process online tickets, banks can't process online transactions, even some emergency services call centres have gone down. The question is, how much damage has been done on a global scale?
So yeah, this is kind of an enormous deal.