IT OT Convergence

DNS

2 min read

What is DNS?

DNS stands for Domain Name System and acts as the phonebook of the internet. It translates human-readable domain names (such as example.com) into IP addresses (such as 93.184.216.34) so that computers can find and communicate with one another.

Without DNS, you would have to remember the numeric IP address for every website.

🧠 How does DNS work?

  1. You type example.com into your browser.
  2. Your device requests the IP address through a DNS query.
  3. The DNS resolver looks this up in several steps:
  • Root server → points to the .com nameserver
  • Top-level domain (TLD) server → points to the example.com nameserver
  • Authoritative nameserver → returns the IP address
  1. The browser connects to that IP address.

🔧 Key DNS records

Record type Function
A Maps a domain name to an IPv4 address
AAAA Maps to an IPv6 address
CNAME Alias for another domain name
MX Points to mail servers
TXT Free text, often used for verification (SPF, DKIM)
PTR Reverse lookup: IP to name
NS Indicates which nameservers are authoritative

🛡️ DNS and security

Risk Security measure
DNS spoofing / cache poisoning Use DNSSEC and trusted resolvers
Exfiltration via DNS tunnelling Monitor and block suspicious queries
Unwanted resolvers Permit only internal resolvers via Firewall or Proxy

🏭 DNS in OT environments

  • Often used in hybrid IT/OT networks
  • Internal DNS management is important for PLCs, HMIs and SCADA systems
  • Air gapped systems sometimes use local DNS via host files
  • ICS equipment is often sensitive to incorrect DNS configurations

📌 In summary

DNS is a foundational protocol that translates domain names into IP addresses. It is essential for network connectivity and reliability — and also an important focus area for Cybersecurity.

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