What Is Dynamic DNS (DDNS)?

Dynamic DNS (DDNS) services keep Domain Name System (DNS) records updated with the correct IP address for websites, devices, APIs, and other web-connected resources that have changing or dynamic IP addresses.

DNS is considered the phone book for the internet, allowing computers and applications to look up the IP address for web domains or devices to which they want to connect.

Every website and device connected to the web has an IP address that allows other devices and applications to find it. IP addresses are typically long strings of numbers or numbers and letters that are difficult for human users to remember. Domain names make it easier to navigate the web, allowing users to enter text like “example.com” rather than numbers and letters like 2600:1401:4000:5b1::b63. The Domain Name System (DNS) is responsible for domain name resolution, translating domain names into IP addresses whenever a user needs to connect to a website or application, or when devices connect to other web resources.

When a user enters a domain name like “example.com” into a web browser, the user’s device sends a request to a DNS server seeking to look up the IP address of the domain name. The DNS request first goes to a recursive DNS server “resolver,” which searches its own cache of previous DNS requests and, if found, responds with the correct IP address. If there is no DNS entry found in the cache, the recursive resolver contacts other nameservers and eventually gets the correct IP address from an authoritative DNS server, which is responsible for keeping track of the official DNS record.

In earlier decades, IP addresses rarely changed, which made it easy for DNS to find or resolve DNS requests for static IP addresses. But as the number of websites, computers, and web-connected devices continued to grow, a shortage of available IP addresses led to the Dynamic Host Configuration Protocol (DHCP). By allowing internet service providers (ISPs) to dynamically assign IPs to users and devices as needed, DHCP addressed the shortage of IP addresses while also providing ISPs with a more cost-efficient way to assign IP addresses.

Dynamic DNS services, or DDNS services, facilitate DHCP by keeping DNS records updated as a website or device’s IP address changes, ensuring that users and other devices will be able to find it.

Organizations often rely on dynamic DNS providers to manage DDNS updates. Typically, DDNS providers use an agent installed on a router or device to update DNS records whenever an IP address changes. This allows DDNS services to map changing IP addresses to web domains and fixed, custom hostnames for computers or IoT devices, for example.

• Cost savings. Dynamic DNS is more affordable for ISPs that have a limited number of IP addresses to assign. As a result, both ISPs and their customers can realize cost savings.
• Security. The DNS enables organizations to configure devices to only allow traffic from certain computers, restricting access to block unauthorized users
• .Automation. By automatically managing changes to DNS records, dynamic DNS resolution enables IT teams to avoid the time-consuming and error-prone processes of manually configuring changes to DNS records.

Dynamic DNS resolution can introduce several security concerns. Threat actors can use the DNS hostnames to more easily evade blocklists that look for specific IP addresses known to be malicious. If attackers can take control of a DDNS update mechanism, they can redirect users to copycat or phishing websites where they may be duped into revealing login credentials, account information, or other sensitive data. Additionally, attackers may leverage DDNS services to change the IP addresses that host command and control servers, making it more difficult for firewalls to detect traffic from these malware-infected devices.