The Internet will crash for millions of people around the world, experts have revealed.
On October 11, the Internet will crash, as the Internet Corporation for Assigned Names and Numbers (ICANN) switches the "root zone" security keys that protect a crucial part of the internet.
This process, called KSK Rollover, is the point at which some users may experience problems and "server failure" error messages.
For anyone affected, the errors might start on October 11 but could also begin 48 hours later.
You won't know if you'll be affected by this problem until October 11
This is because many of the servers that manage the Internet keep a cached version of requests for two days after the last successful attempt is made.
The root zone might sound like something out of a Hollywood movie about hacking, but in reality it's just final part of the web address you type in to your browser.
Across the world these are administered by different companies.
Perhaps the most famous is .com - run by VeriSign. The UK's root is administered by Nominet.
The root zone was first secured with encryption keys in 2010.
The old key is called KSK-2010 while the new one is KSK-2017.
On October 11 KSK-2010 will cease to be valid - the Internet equivalent of changing the locks on your front door.
So why all this fuss anyway? Well, the root zone security keys are designed to ensure that it's not possible for malicious users to make changes and potentially hijack parts of the internet.
These keys are being changed now because it's theoretically possible for powerful computers to guess encryption codes, given enough time.
This renewal might be the first, but it won't be the last.
Will it affect you?
In reality most users will see no change to the Internet browsing.
ICANN runs both old and new keys at the same time so Internet providers can test their networks to ensure no such breakages occur.
Mistakes do, of course, happen but for the most part the Internet has been designed to be a resilient system.
ICANN says that only one per cent of Internet users are likely to have any problems.
Even so, with the Internet population now at 3.58 billion users, that could mean that nearly 36 million users could be affected globally.