What is DNS? (and how it makes the Internet work)

Summary

This script offers an insightful exploration into the Domain Name System (DNS), a critical internet infrastructure that translates human-friendly website names into IP addresses. It uses an analogy of a phone's contact app to explain how DNS servers resolve domain names to IP addresses, highlighting the process's complexity and potential vulnerabilities. The script also discusses DNS security, introducing solutions like DNS over HTTPS (DOH) and DNS over TLS (DOT), and touches on various DNS record types, emphasizing their importance in internet operations. It concludes with a teaser for a follow-up on ethical hacking of DNS.

Takeaways

• 🌐 The Domain Name System (DNS) is essential for translating human-friendly website addresses into IP addresses that computers understand.
• 🔍 When a browser can't find a website's IP address in its cache, it queries a DNS server, which acts like a phone book for the internet, mapping domain names to IP addresses.
• 🔄 The DNS resolution process can involve multiple steps, including querying a stub resolver, recursive DNS servers, root servers, and authoritative name servers.
• 🔒 DNS queries can be insecure, as they are sent in plain text over UDP port 53, making them susceptible to interception and spoofing by hackers or ISPs.
• 🔒🔒 DNS over HTTPS (DOH) and DNS over TLS (DOT) are methods to secure DNS queries by encrypting them within HTTPS or TLS connections, protecting user privacy and preventing DNS spoofing.
• 🏠 Users can run their own local DNS server, which can provide a cache of frequently visited websites and forward unknown queries to an upstream DNS server.
• 🛡️ Twin Gate offers secure DNS features as part of its VPN replacement service, allowing users to enforce DOH and even add DNS filtering for additional security.
• 📝 DNS records come in various types, including A records for IP address mapping, MX records for email server identification, and TXT records for additional data or security purposes.
• 🔑 The Internet Corporation for Assigned Names and Numbers (ICANN) governs DNS and accredits domain registrars, which are companies authorized to sell domain names.
• 🕵️‍♂️ WHOIS is a protocol used to query databases that store the registered users or assignees of domain names and IP address blocks, although privacy protections can redact some information.
• 💡 DNS is not only about domain-to-IP address mapping; it plays a crucial role in email security, content filtering, and can even prevent access to malicious websites.

Q & A

What is the purpose of the Domain Name System (DNS)?

The purpose of DNS is to translate human-friendly domain names, such as 'example.com', into IP addresses that computers use to identify each other on the internet.

How does a web browser resolve a website's IP address when the user enters a URL?

The web browser uses a process involving DNS servers to resolve the IP address. It starts with a local cache check, then queries a configured DNS server, which may be recursive and query other DNS servers until it finds the authoritative server that can provide the IP address.

What is a stub resolver in the context of DNS?

A stub resolver is the DNS client running on a local machine. It's responsible for sending DNS queries to a DNS server and receiving the responses, but it doesn't perform the full resolution process itself.

What is a recursive DNS server, and how does it differ from other DNS servers?

A recursive DNS server is one that performs the full resolution process on behalf of the client. It will make multiple requests to various other DNS servers if necessary to find the IP address associated with a domain name, unlike a stub resolver which only sends queries to a DNS server.

What are the 'mafia bosses' of DNS, and what role do they play?

The 'mafia bosses' of DNS are the root servers at the top of the DNS hierarchy. They manage the top-level domains (TLDs) and delegate queries about specific TLDs to other authoritative DNS servers responsible for those domains.

How does the DNS process ensure that the user is directed to the correct website?

The DNS process ensures the correct website is directed by a series of queries that end with the authoritative DNS server providing the exact IP address associated with the requested domain name. This process is based on a hierarchy of DNS servers, each with a specific role in resolving domain names to IP addresses.

What is DNS spoofing, and how can it be a security risk?

DNS spoofing is a type of cyber attack where a malicious actor intercepts DNS queries and returns false IP addresses, redirecting the user to a different, often malicious, website. It's a security risk because it can lead to phishing, malware distribution, and other forms of cybercrime.

What is DNS over HTTPS (DOH), and how does it improve DNS security?

DNS over HTTPS (DOH) is a protocol that encrypts DNS queries and responses, making them secure and private. It prevents eavesdropping and manipulation of DNS data by using the HTTPS protocol, which is commonly used for secure web browsing.

What is Twin Gate, and how does it relate to DNS security?

Twin Gate is a remote access solution that includes features for secure DNS. It allows users to enforce the use of DOH on devices within its network, ensuring that DNS queries are encrypted and secure, even when connecting from remote locations.

What are the different types of DNS records mentioned in the script, and what are their functions?

The script mentions several DNS record types: A records for domain-to-IP mappings, NS records for indicating authoritative DNS servers for a domain, AAAA records for IPv6 address mappings, MX records for email server identification, PTR records for reverse DNS lookups, CNAME records for domain aliases, and TXT records for arbitrary text data, often used for email authentication and other purposes.

What is the role of ICANN in the DNS ecosystem?

ICANN, the Internet Corporation for Assigned Names and Numbers, is responsible for governing DNS and ensuring its smooth operation. It accredits domain registrars and has the authority to delegate who can become a TLD server.

How can an individual secure their DNS queries at home?

An individual can secure their DNS queries at home by setting up a local recursive DNS server, such as one running ad guard or Pi-hole, which can block ads and provide local caching. They can also configure their devices to use secure DNS servers that support DOH or other secure protocols.