How DNS Attacks Work?

How DNS Attacks Operate

The Domain Name System (DNS) is a critical part of Internet infrastructure that translates human-readable domain names (like example.com) into IP addresses (like 93.184.215.14), which computers use to identify each other on a network. Without DNS, users would need to remember complex numerical IP addresses to access websites. In this way, DNS acts as the Internet’s phonebook, making it convenient for humans to navigate the web using domain names instead of long numbers.

The Domain Name System consists of millions of hierarchically structured DNS servers that play distinct roles in resolving domain names, handling trillions of DNS queries every single day. As this system is ubiquitous and vital for the normal functioning of the Internet, DNS is frequently targeted or exploited in various types of cyberattacks. In this post, we will explore the most common DNS-related threats.

DNS Hijacking

DNS hijacking, also known as DNS redirection, occurs when attackers manipulate the DNS resolution process to redirect users from legitimate websites to fraudulent ones. The basic idea behind DNS hijacking is to replace the IP address of the legitimate resource that the user is trying to reach with the IP address of a malicious resource.

There are different ways DNS hijacking can occur. One method is local DNS hijacking, where attackers modify DNS settings on a user’s device or router, redirecting DNS queries without the user’s knowledge to a name server controlled by the attacker.

Another approach involves using a Man-in-the-Middle (MitM) technique to intercept communication between users and a legitimate DNS server, altering the server’s responses. Attackers may also directly compromise DNS servers, causing them to redirect multiple users simultaneously.

The consequences of DNS hijacking can be severe, leading to financial loss, data breaches, and privacy violations. Preventing it requires securing DNS infrastructure with protocols like DNSSEC, which ensures the authenticity of DNS responses, and locking down DNS settings on devices and routers to prevent unauthorized modifications. Additionally, regular monitoring and updates to DNS configurations can help safeguard against DNS hijacking attacks.

DNS Cache Poisoning

Another method attackers use to redirect users is DNS cache poisoning. Attackers inject fraudulent DNS records into a recursive resolver’s cache (hence the term cache poisoning). As a result, the DNS resolver associates certain domains with false IP addresses, misleading users into visiting malicious websites instead of legitimate ones.

As in the case of DNS hijacking, the consequences of DNS cache poisoning can be very serious, including successful phishing attacks or malware infections that lead to the theft of sensitive data, such as login credentials or financial information. Since the attack relies on IP address spoofing rather than fake domain names, it becomes much harder for users to detect the danger. This subtle redirection greatly increases the likelihood of users falling victim to the attack.

Preventing DNS cache poisoning requires implementing DNSSEC to verify the authenticity of DNS responses. Proper name server configuration and continuous monitoring also reduce the risk of DNS spoofing attacks.

DNS Tunnelling

In addition to attacks targeting DNS infrastructure, there are also malicious techniques that exploit the technology’s flaws to benefit attackers. One such method is DNS tunneling, which abuses the DNS protocol to carry non-DNS traffic through DNS queries and responses. This technique can be used to bypass firewalls and exfiltrate sensitive data.

Attackers set up a malicious DNS server under their control and encode the data they wish to send from the victim’s network into DNS requests and the data sent back to the network into DNS responses, establishing a covert communication channel. Since DNS traffic is typically allowed through most firewalls, DNS tunneling is particularly effective for smuggling data out of restricted networks or enabling unauthorized remote access.

To detect and restrict DNS tunneling, it’s essential to monitor for unusual or excessive DNS traffic. Implementing strict filtering policies, using DNS firewalls, and analyzing query patterns can help identify suspicious activity. DNS tunneling utilities that monitor for unusual behavior can further improve detection.

DNS Amplification DDoS Attacks

Another way attackers can exploit DNS infrastructure is by using it to launch Distributed Denial of Service (DDoS) attacks. A DNS amplification attack is a specific type of DDoS attack in which attackers send small DNS requests to a large number of vulnerable DNS servers, spoofing the source IP address to make it appear as though the requests are coming from the target. The DNS servers then respond with much larger replies, overwhelming the target with traffic and causing a denial of service.

This attack, also known as DNS reflection, works by exploiting the disparity between the size of DNS requests and responses. Since DNS queries are typically small but responses can be significantly larger, attackers can amplify the volume of traffic directed at their target without requiring substantial bandwidth on their part. Open DNS resolvers act as reflectors, multiplying the attack’s impact with an amplification factor of up to 100:1. This means a small request can result in a much larger response, greatly increasing the attack’s effectiveness.

The best way to protect an organization’s digital infrastructure against DNS amplification attacks, as well as other types of DDoS attacks, is to use a cloud-based solution like Qrator.AntiDDoS. With a global network of 15 strategically placed traffic scrubbing centers, this approach provides the redundancy, reliability, and capacity needed to effectively handle even large-scale attacks.

DDoS Attacks on DNS Servers

Beyond being used to facilitate DDoS attacks on other targets, DNS servers themselves can become direct victims of DDoS attacks. One particular example is the NXDOMAIN attack, also known as a DNS water torture DDoS attack, where attackers bombard a name server with a large volume of requests for non-existent or invalid DNS records.

Attacks like this overwhelm the DNS server with a flood of requests, preventing it from processing legitimate DNS queries and causing significant disruptions to online services. By targeting name servers, attackers can make websites and services effectively unreachable, even when the web servers remain fully operational. That’s exactly what happened in 2016 during a series of massive DDoS attack on DNS provider Dyn, which resulted in dozens of major web services, such as Airbnb, Twitter, and Spotify, being unavailable for hours.

Qrator.SecureDNS offers effective DDoS protection by leveraging a global Anycast network, ensuring high availability and performance at no extra cost. By distributing DNS traffic across multiple global servers, Anycast provides resilience and improves response times by routing DNS queries to the closest server.

Additionally, Qrator.SecureDNS supports DNSSEC, ensuring secure DNS queries. The service can be deployed as a secondary DNS server or through Qrator DNS Reverse Proxy, offering flexibility and seamless integration with existing infrastructure while maintaining advanced protection.