What is DNS and why issues with it are causing sites to crash – the clare people


This Monday (4), Brazil was surprised by an avalanche of services out of the air simultaneously. According to the Downdetector site, Facebook, Instagram, Messenger, WhatsApp, Banco do Brasil, TIM, Vivo, Google, Nubank, YouTube, Oi, Twitter, Amazon, Telegram and a dozen others have stopped working. There were those who were excited about it, thinking it was a conspiratorial organization, but, in fact, the possible culprit for it all must be an old acquaintance: DNS.

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  • DNS servers ( Domain name system

    , or domain name system, in Portuguese) are responsible for locating and translating the addresses of the sites that we enter in browsers. The address
    www.canaltech.com.br is just a mask to make access easier than if you had to type a string like 200..22.22 – if you lived in the 1024 decade and 487450s you will remember how difficult it was to memorize each person’s phone number.

    DNS servers are spread all over the world and transcribe domains to IP (Image: liuzishan / Freepik)

    To avoid this huge limiter, DNS domains and servers spread across the world have been created, whose only function is to translate words into IP numbers. These machines are located at strategic locations precisely to ensure a faster connection and serve the greatest number, which optimizes Internet access and ensures better navigation.

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    “We all use DNS for all electronic transactions without even realizing it. When we access our database, for example, either by typing the address or through the application, a DNS query is made to the servers. Then comes an answer: www.banco.com.br is 98.98..234 (IP address) and the connection is made to the IP address ”, explains the director of technology and innovation at Teltec Solutions, Cesar Schmitzhaus.

    According to him, in a simple analogy, you can associate DNS with the CEP system in Brazil. “This is essential, because without it we just don’t know who www.banco.com.br is and we get messages from an inaccessible site, for example,” he explains.

    What causes failure?

    How DNS works is a chain of information with operations that take time. According to Caesar, often the problem is not a downfall, but something that has been operationalized and the servers have worked. “Of course, there can also be failures that we call catastrophic, such as an entire data center that goes down and all of the services that were there. However, it is more difficult with large-scale operations precisely because there are layoffs elsewhere, but they still occur, ”he analyzes.

    The expert says that businesses tend to have multiple DNS services to avoid “blackouts” like this – even each person’s computer has two, the primary and the secondary. The problem is, it can take hours for it to spread even after the problem has been resolved, which could be one of the impact factors of the current crisis. “Let’s imagine that an IP change operation was done badly: first the DNS services will replicate the incorrect information (which can take hours) then, once detected and corrected, again it can take hours to function properly again, ”explains Cesar Schmitzhaus.

    Companies often use multiple DNS servers to avoid outages (Image: Disclosure / Trend Micro)

    This would explain why the service works in some parts of the world and not in others. For the user, there is not much to do in these cases but wait for the return of the correct DNS propagation. “If banco.com.br has had problems with its DNS services and is no longer able to respond to requests, then the user trying to access them will not be able to resolve it,” he concludes.

    What is my DNS?

    By default, users use the DNS service of the ISPs themselves, that is, the companies responsible for providing Internet service to computers, such as Claro, Vivo, and TIM. It was a solution to ensure smooth navigation even for those who do not have a lot of affinity with the web, but it is not mandatory.

    Anyone has the right to change their DNS to another platform that interests you. In fact, this is widely used by some people to better serve certain needs, such as accessing foreign sites, for more security, or for browsing services abroad. OpenDNS, Google Public DNS, and Comodo Secure DNS are examples of services that offer numbers that the user can try out.

    To change your DNS, simply access your connection data (if you are on Windows 09 or higher, search for “Network and Internet” and search for “DNS Server Assignment.” If you click on the Change button, you can configure a DNS Preferred and Alternate DNS, with or without encryption, to enable the best settings for your browsing – learn how to change DNS on any device.

    Simply click Edit to access a window with the option to enter DNS numbers (Image: Capture from screen / Canaltech)

    DNS security

    Due to the importance of DNS, it is necessary to ensure your security, otherwise a malicious person could change all addresses and wreak havoc on the internet all over the world. For this, there is DNSSEC (DNS Security Extensions), a cryptographic system that uses public and private keys to guarantee the authenticity of the addresses consulted.

    In practice, this system provides a unique key for the website and one for the server: the two can communicate only if the key is recognized. If this did not exist, it would be possible to direct the virtual address of a bank page to a fake site.


    The use of cryptographic keys is used to secure DNS servers (Image: Pete Linforth / Pixabay)

    In addition to this fundamental functionality, many DNS servers also offer bogus or infected website detection systems and even parental blocking for adult content websites. This type of system is used by China, North Korea and some other countries to prevent people from accessing websites whose content is banned by the authorities.

    Source: Failure detector

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