The Domain Name System (DNS) plays a pivotal role in the seamless functioning of the Internet. However, this critical infrastructure is susceptible to Denial of Service (DoS) and Distributed Denial of Service (DoS) attacks. These attacks can significantly disrupt the online services that depend on DNS, leading to substantial financial and reputational losses for businesses. This blog post aims to demystify DNS DoS attacks against DNS, explain their impact, and outline strategies to mitigate these threats.
What is DoS Attack against the DNS?
A DoS attack aims to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services. When it comes to DNS, a DoS attack seeks to overwhelm DNS servers with malicious traffic, rendering them incapable of responding to legitimate DNS queries. A Distributed Denial of Service attack is similar but involves multiple compromised systems being used to target a single system, making it more challenging to mitigate.
How does DoS against the DNS happen?
As a foundational component of the internet, DNS translates human-readable domain names into IP addresses, allowing users to access websites and other services effortlessly. By overloading DNS servers with a flood of malicious network traffic, attackers aim to disrupt this translation process, effectively making websites inaccessible.
Cybercriminals can exploit vulnerabilities in the DNS infrastructure and the deployment of a specific domain, such as inadequate server capacity, insufficient network connectivity, or missing DoS and DDoS protection, to succeed with their attacks. By overwhelming the DNS servers with excessive traffic, attackers can prevent legitimate users from accessing services, causing significant service disruption and potential financial and reputational damage to the affected organization.
In the case of a DoS (Denial of Service) attack against DNS (Domain Name System) servers, several types of DoS or DDoS (Distributed Denial of Service) vectors can be effective. For instance, NTP (Network Time Protocol) amplification involves exploiting the NTP servers to overwhelm the target with traffic, while HTTP GET floods target web servers by sending numerous requests. These attacks do not necessarily require DNS-specific network traffic to disrupt the DNS services.
Some DoS and DDoS attacks use DNS as an attack protocol to generate a large amount of network throughput or DNS queries against DNS or any other target. When targeted against a DNS server, mitigation becomes more complex because the technology must distinguish between several types of DNS packets. Two of the most common attacks using DNS as an attack vector include:
DNS Flood Attacks
This involves sending an overwhelming number of queries to a DNS nameserver, exhausting its resources. Attackers often use botnets to disguise their traffic and avoid detection. A popular DNS flood method is the NXDOMAIN attack, where attackers generate excessive requests for non-existent domains, overwhelming the nameserver and depleting the resolver’s cache.
DNS Amplification Attacks
In this type of attack, the attacker sends a DNS request with a spoofed IP address of the target, causing the DNS server to flood the target with large responses. This method amplifies the attack’s impact without requiring significant resources from the attacker.
Examples of DoS against the DNS
One of the most notable DNS-related DDoS attacks (Distributed Denial of Service) occurred in 2016 when a major DNS provider became the target of a large-scale attack. The attack severely disrupted internet services across the United States, affecting major social media platforms and other types of websites. This incident illustrated the profound impact that disruptions to DNS infrastructure can have on internet accessibility and business operations.
Vercara’s UltraDNS platform frequently receives DoS and DDoS attacks as attackers attempt to DoS one of our customers. UltraDNS experienced 1,509 DDoS attacks in the first half of 2024, marking a 56.05% increase from the previous year. These attacks accounted for 4.54% of all observed DDoS incidents. The largest attack registered over 38.28 Gbps and lasted just over eleven minutes. These statistics highlight the growing threat of DNS-focused DDoS attacks on DNS and underscore the need for adequate protection.
How DoS against the DNS impacts your business
Disruptions caused by DoS against DNS servers not only hinder user access but also impose a ripple effect across the internet, affecting the performance of web services and applications that rely on DNS.
A successful DoS attack on DNS DoS attack can have severe consequences for businesses:
- Service Disruption: Critical services relying on DNS resolution may become inaccessible or have intermittent latency during an attack, resulting in lost revenue and customer trust.
- Operational Downtime: Businesses may need to divert resources to mitigate the attack, leading to operational inefficiencies.
- Reputation Damage: Frequent service interruptions can harm a business’s reputation, leading to long-term financial repercussions.
- Customer Churn: Prolonged service disruptions can frustrate customers, leading them to switch to competitors. This loss of customers further impacts revenue and may require considerable effort and resources to address and recover lost loyalty.
Preventing DoS against the DNS
While mitigating DNS DDoS attacks without affecting legitimate traffic is challenging, several strategies can enhance protection:
- Anycast DNS Network: Deploying a geographically distributed anycast DNS network across many points of presence (PoPs) can absorb large-scale attacks by spreading the traffic across multiple locations.
- Use a DDoS Mitigation Service: Implementing a DDoS mitigation service can be an effective method to detect and defend against DDoS attacks targeting DNS infrastructure. These services identify malicious traffic patterns and filter them out before they reach your network, ensuring legitimate traffic can proceed smoothly without interruption.
- Use Disparate DNS Providers: Leveraging multiple DNS providers can provide redundancy and reduce the risk of complete service disruption during an attack. By diversifying DNS services, if one provider experiences a failure due to a DDoS attack, the others can continue to handle requests, ensuring continued operation and availability. This approach also adds complexity for attackers, as they need to target different networks simultaneously to have a significant impact.
- Increase Resource Record Time-to-Live (TTL): By increasing the TTL of DNS resource records, businesses can reduce the frequency of queries reaching authoritative nameservers as recursive servers cache answers. This caching mechanism serves as a shock absorber to any kind of short-term DNS outage and helps to conserve bandwidth.
- Disable DNS ANY Requests: Disabling DNS ANY requests can prevent attackers from exploiting this record type for amplification attacks.
- Implement Advanced Rate Limiting: Sophisticated DNS servers can utilize advanced rate-limiting techniques, such as queuing requests from specific resolvers to conserve bandwidth during spikes in traffic.
Everything depends on DNS
DoS and DDoS attacks on DNS pose a significant threat that can disrupt essential online services and impact businesses. These attacks have led to numerous notable incidents. By implementing proper controls and managing risks, domain and website owners can mitigate the effects of DNS DoS attacks. Businesses must remain vigilant and adapt their defenses to safeguard their DNS infrastructure from evolving threats.
How Vercara can help protect DNS servers from DoS & DDoS attacks
Vercara’s UltraDNS is a robust authoritative DNS service designed to safeguard against compromises and DDoS attacks on DNS servers. It offers advanced security features and reliable performance, ensuring your domain name system remains secure and efficient. UltraDNS is further protected by UltraDDoS Protect to maintain availability. UltraDNS platform frequently receives DoS and DDoS attacks as attackers attempt to DoS one of our customers. UltraDNS experienced 2,214 DDoS attacks in 2024, a 29.07% increase from the previous year. The largest attack registered over 294.37 Gbps and lasted just over one hour. These statistics highlight the growing threat of DNS-focused DDoS attacks on DNS and underscore the need for adequate protection.
Vercara’s UltraDNS2 is an add-on service of UltraDNS that provides exceptional service-level redundancy with two distinct DNS anycast resolution networks, delivering enhanced value.
Vercara’s UltraDDoS Protect is a specialized DDoS mitigation solution offering comprehensive protection through on-premises hardware, cloud-based DDoS mitigation, or hybrid models. Tailored to fit organizational needs, Vercara’s DDoS Protection services include blocking and redirecting DDoS attacks, and cloud DDoS prevention, providing extensive and adaptable defense services.
To learn more, explore our advanced security solutions and connect with our cybersecurity experts to enhance your defenses against DDoS attacks and other emerging threats.
