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Retrospective · Worldwide, October 2021 · published

The six hours Facebook disappeared from the internet

Эта статья на английском языке.

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On 4 October 2021, Facebook, Instagram, WhatsApp and Messenger disappeared for billions of people for about six hours. No country went offline and no one attacked them. One routine command took a whole company off the map of the internet.

What happened

  • 4 Oct 2021, about 15:40 UTC During routine maintenance, engineers ran a command meant to check the capacity of Facebook's private backbone network. It accidentally disconnected the backbone, and a bug in the tool that should have stopped it let it through.
  • Moments later Facebook's DNS servers, which are built to withdraw their routes when they lose contact with the data centres, did exactly that. Cloudflare saw the routes to all of Facebook's name servers withdrawn at 15:39 UTC. The rest of the internet could no longer even find facebook.com.
  • The afternoon With internal tools down too, engineers had to get physical access to data centre equipment to fix it.
  • 21:05 – 22:45 UTC The name became reachable again around 21:05 UTC, and services were broadly back by about 22:45 UTC.

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Why it mattered

In many countries WhatsApp is the phone network: families, shops, doctors and even governments run on it. For six hours that was gone, and other services slowed down under the flood of people and apps retrying. It showed how much of daily life depends on a few companies, and that the worst outages often come from inside, not from attackers.

What Blackout Map would show

Every country's internet kept working, so the map would stay green, which is correct: this was a service outage, not an internet outage. Our website checks are where it would appear: facebook.com, instagram.com and web.whatsapp.com would fail with a name that no longer resolves, and the "Is it down?" pages would fill with reports from everywhere at once.

Sources

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Blackout Map is a live map of internet outages and shutdowns around the world. Open the map · Security watch · RSS · Follow us on X: @Blackoutmap_net

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