What is DNS Poisoning? How to Prevent DNS Spoofing Attacks

As we increasingly rely on the internet for both personal and professional activities, understanding the potential threats to our online security becomes essential. A prevalent and significant risk is DNS poisoning, a cyberattack that manipulates and exploits vulnerabilities in the Domain Name System (DNS).

This article explains how DNS poisoning works, illustrating its impact on organizations and common attack methods. Additionally, we’ll offer insight into effective strategies for preventing these attacks to keep networks safe and secure.

But before we explain how DNS poisoning works, it’s important to understand how the DNS normally functions. 

What Is DNS and How Does It Work?

The Domain Name System (DNS) is a tool that serves as the Internet’s phone book, converting standard human-friendly domain names, such as (www.example.com), into machine-readable IP addresses, such as 192.0.2.37. This is achieved through a DNS lookup process where a DNS server, functioning like an automated directory assistance service, interprets the domain names into their corresponding IP addresses.

When you type a URL into your browser, the DNS system translates it into the specific IP address where the website is hosted, allowing your browser to access and load the requested webpage.

This process happens between four different servers:

How the 4 Types of DNS Servers Locate IP Addresses

Each of these four types of servers play a uniquerole in IP address retrieval. Here’s how normal DNS communication works:

1. DNS resolvers: When a web client sends a DNS query, the DNS resolver (also known as recursive resolver) either delivers cached data or sends the request to the remaining servers in order to deliver the IP address.
2. Root nameservers: After receiving a request from a DNS resolver, the root nameserver interprets the domain’s extension and directs the request to the appropriate top-level domain (TLD) nameserver.
3. Top-level domain (TLD) nameservers: In response to requests from root nameservers, TLD nameservers locate the specific domain, then send a request to that domain’s authoritative nameserver. There are unique TLD nameservers for every domain extension: .com, .org, .gov, and so on.
4. Authoritative nameservers: The authoritative nameserver holds IP information for individual domain names; after receiving a request from a TLD nameserver, the DNS resolver receives the associated IP address from the authoritative nameserver.

Since nearly all modern networks use this process to access DNS records, it’s crucial to avoid attacks by maintaining secure best practices.

What Is DNS Poisoning?

DNS poisoning is a type of cyberattack that manipulates the DNS server or DNS cache, injecting it with fraudulent address resolutions that redirect users to illegitimate sites. 

As a result, when a user makes a DNS request for a specific website, the DNS resolver unknowingly redirects the request to a completely different IP address, often a malicious website set up by the hacker. The unsuspecting user, thinking they’re logging into a legitimate website, may then inadvertently provide personal information or login credentials, falling prey to data theft or malware installation.

DNS poisoning attacks are a serious threat to internet security, with the potential to disrupt operations and compromise data at both individual and organizational levels. Understanding how these attacks work allows for better strategies for mitigating risks and ensuring a safer browsing environment.

DNS poisoning is sometimes called DNS cache poisoning or DNS spoofing, but this is a mistake; DNS cache poisoning and DNS spoofing are specific types of DNS poisoning. Next, we’ll explore the differences in more depth.

DNS Poisoning vs. DNS Cache Poisoning vs. DNS Spoofing

While DNS poisoning, DNS cache poisoning, and DNS spoofing are often used interchangeably, they have subtle differences.

• DNS poisoning is a broad term encompassing any attack that introduces incorrect IP addresses into the DNS. It may also be called domain poisoning.
• DNS cache poisoning specifically refers to cases of DNS poisoning where the attacker corrupts the DNS cache data, leading to misdirected queries.
• DNS spoofinginvolves the attacker responding to a DNS request with false data, causing the server to forward traffic to an incorrect or malicious IP address, hence orchestrating a successful deception.

DNS Hijacking vs. DNS Poisoning

While both DNS hijacking and DNS poisoning are malicious techniques used by hackers to divert internet traffic, they operate in different ways. We’ve seen that in DNS poisoning, the attacker introduces corrupt DNS data into the DNS resolver’s cache, causing the name server to return an incorrect IP address. 

In DNS hijacking, the attacker redirects queries to a different DNS server. It usually involves the alteration of the local host files or the manipulation of the router. The purpose of this attack is to lead users to fraudulent websites, where the attacker can steal sensitive data, such as usernames, passwords and credit card information. For example, a user may think they are visiting their online banking website when, in fact, they are being redirected to a fake version of the site created by the hacker.

DNS Hijacking is more about taking control of the server to redirect traffic, while DNS Poisoning is about corrupting the data within the server to misdirect web traffic. Both these attacks are threats to user privacy and data security.

Components of DNS Cache Poisoning Attacks

To understand how DNS poisoning works, we first need to explore how DNS resolvers, DNS caching and related protocols work.

DNS Resolvers

At the heart of DNS operations lie DNS resolvers. These are devices or software applications that perform DNS lookup, i.e., they acquire the IP address corresponding to a domain name. Every time a user types in a web URL, it is the DNS resolver that facilitates the actual, machine-understandable IP address from the domain name.

DNS Caching

To expedite this process of address resolution, DNS resolvers rely upon a temporary database known as DNS cache. This cache stores the details of all recent and attempted website visits, reducing the DNS lookup time for frequently visited sites by fetching IP addresses directly from the cache instead of initiating a fresh lookup.

User Datagram Protocol (UDP) vs. Transmission Control Protocol (TCP)

The DNS record lookup process relies on User Datagram Protocol (UDP) — a transport layer protocol that sends datawithoutfirstconfirming a connection. Since communications are transmitted whether or not a connection is established, UDP communications can be vulnerable to interception.

An alternate protocol called Transmission Control Protocol (TCP) requires an established connection between the user and the target, verified and maintained from initial request through final response.

How Do DNS Poisoning Attacks Work?

DNS poisoning exploits the internet’s phonebook (the DNS) through the lookup process that lets your browser translate a website URL into a numeric IP address. If a user’s DNS resolver doesn’t have the website’s IP address saved, it accesses the DNS to find it — and that’s when DNS poisoning occurs.

Attackers impersonate DNS nameservers. When a user attempts to access a website with a legitimate domain name, their DNS resolver queries a DNS nameserver to request that domain’s IP address. The fraudulent nameserver responds with an illegitimate IP address, which sends the user to the wrong website.

Since DNS uses connectionlessUDP to communicate, attackers can easily send these messages, knowing DNS resolvers will automaticallyaccept the response.

Here’s exactly how DNS poisoning works:

Step 1: User Attempts to Visit a Website; DNS Resolver Requests IP

To visit a specific website, a user requests the IP address by entering the domain name into their browser — say, samplesite.com.

When the browser hasn’t visited that website before, it requests the IP address for samplesite.com by reachingout to a DNS resolver. That DNS resolver expects to receive a legitimate IP address from the authoritativename server.

Step 2: Attacker Intercepts DNS Request, Redirecting the User

Here lies the crux of DNS poisoning attacks, where attackers must respond to DNS requests faster than the authoritative server.

Attackers intercept DNS requests by immediately flooding the resolver with falseresponses before the reply from the authoritative nameserver arrives. In these replies, they substitute authentic IP addresses with false ones.

For example, if the real IP address for samplesite.com were 192.0.2.37, the attacker might deliver a fake IP address of 192.0.2.36 instead. Because the User Datagram Protocol (UDP) doesn’t verify DNS data integrity, DNS resolvers believe these responses come from the authoritative nameserver — and accept the false IP addresses as legitimate, redirecting users to malicious sites.

Satisfied with the response, the DNS server caches that false IP address and sends it straight to the user. While the user’s intended destination was samplesite.com at IP address 192.0.2.37, the DNS server sends them to a spoofed site with the IP address 192.0.2.36 instead. 

That fake website might look identical to samplesite.com, tricking the user into browsing, clicking links, and entering sensitive information, all of which the attacker can intercept.

Step 3: False IP Address Poisons the DNS Cache

Once the server accepts the fake website and IP, it caches the illegitimate IP address for future use. That’s how attackers poison DNS caches.

When the user attempts to visit that website again, the DNS resolver looks up the poisoned DNS cache and retrieves the same wrong IP address from the initialvisit — thus perpetuating the attack.

But it doesn’t end there. When organizations used shared caches, these attacks don’t just affect a single DNS server. By caching the same false IP addresses across devices, these poisoning attacks can impact the entire company.

Step 4: Poisoned Cache Spreads to Other DNS Servers

Since DNS caches regularly share information with other DNS servers to keep their data updated, a poisoned DNS cache can spread its corrupteddata to other caches.

This propagation of false DNS information across multiple domain name servers amplifies the impact of the attack, leading to a more widespread compromise of user data and network security. Consequently, the user is redirected to a maliciouswebsite controlled by the attacker instead of the intended site.

This switch often goes unnoticed, and unsuspecting users, thinking they’re on the legitimate site, may input their sensitive data, providing the attacker with an opportunity for data theft or malware installation. In this way, a single successful DNS poisoning attack can impact multiple users who all share the same DNS cache.

Every cache entry has a specific time to live (TTL), which determines how long a server stores that data before it expires. So, unless a network administrator or user clearsthecache, the false IP address and poisoned cache will live on, continuing to redirect users to fake sites.

Real-World Examples of DNS Poisoning

DNS poisoning is common and dangerous. These are actual examples of high-profile DNS attacks.

• China server leak (2010): Chinese servers overtook international DNS resolvers, redirecting users attempting to visit sites like Facebook, Twitter, and YouTube to illegitimate sites. It started when China knowingly inflicted DNS poisoning on itself to censor social media nationally.
• Malaysia Airlines (2015): Hackers known as Lizard Squad redirected traffic away from the legitimate server of the Malaysia Airlines website. When users attempted to log in, they received a 404 error with an image of a lizard. While the airline assured the public that no data was compromised, hackers released screenshots of passenger booking pages with names, email addresses, and phone numbers.
• MyEtherWallet (2018): Hackers compromised Amazon Web Services (AWS) with a DNS poisoning attack impacting several domains, including cryptocurrency website MyEtherWallet. By redirecting traffic to a fake website that captured users’ login credentials, the hackers gained access to user accounts and stole about $17 million worth of Ethereum.
• DNS Hijacking by APT28 (2026): DNS hijacking by APT28 and Forest Blizzard, known Russian intelligence actors, exploited Small Office/Home Office (SOHO) routers to execute man-in-the-middle (MITM) The APT28 attacks led to widespread password and OAuth token theft.

DNS Spoofing Attack Methods

While DNS spoofing attacks can cause serious security concerns, having a grasp of them can help you anticipate, recognize and thwart potential threats. Some common DNS spoofing methods include:

Interception of DNS Requests

In this method, attackers intercept DNS queries in transit from the DNS resolver to the DNS server. By doing this, they gain the ability to return fake DNS responses. The manipulated DNS server then unknowingly directs unsuspecting users to malicious sites, facilitating potential data theft or malware installation.

DNS Server Overloading

In a technique akin to a denial-of-service (DoS) attack, attackers target vulnerable DNS servers, overloading them with multiple simultaneous DNS requests. The server, unable to handle the load, crashes, giving attackers an opportunity to poison the DNS cache with malicious IP addresses.

Exploiting Insecure DNS Configuration

If a DNS server is improperly configured or lacks robust security measures, attackers can exploit these weaknesses to perform DNS spoofing. Here, vigilance in maintaining updated and secure DNS configurations is essential to prevent DNS poisoning attacks.

Man-in-the-Middle Attack

During a man-in-the-middle (MITM) attack, an outsider intercepts DNS queries in transit between the client and the server, manipulating the data so the client connects to the attacker’s server. By controlling the server to which the client connects, attackers can further their malicious agenda.

Pharming Attack

In a pharming attack, attackers manipulate a website’s host file or domain namesystem to redirect users to a fraudulent website, even when they’ve typed the correctaddress into their browser.

Risks of DNS Poisoning Attacks

DNS poisoning attacks have severe implications for organizations, including: 

• Credential theft: When users log in to a fraudulent site, attackers can easily steal their login credentials (usernames and passwords).
• Malware: Simply by visiting a fake website or clicking seemingly innocent links on pages, users can inadvertently install malware on their devices. Malware such as ransomware, spyware and trojans can control devices and steal data without a user’s knowledge.

• Falsified security software updates: One form of DNS poisoning spoofs security provider websites. When this happens, users falsely believe they’ve downloaded the latest updates and patches — but instead, they remain vulnerable to continued attacks, new viruses and malware.
• Data and identity theft: Significant data theft is a common fallout, as the attack can expose confidential customer information, intellectual property or sensitive internal data.
• Damaged reputation: Organizations can also face reputational damage, leading to loss of customer trust and potential business. 
• Financial loss: The subsequent financial implications of lost business can be debilitating. When customers or clients disappear, it can be difficult or impossible to recover. This affects revenue, profit margins, projections, and the involvement of new or existing investors. 
• More severe cyber threats: Moreover, the infiltration into the organization’s network poses a threat of escalated cyberattack severity. On its own, a spoofed website isn’t dangerous — but the potential to infect a device, network, or entire organization can be devastating.
• Recurring issues: Once a device caches an illegitimate IP address, every attempt to visit the real website will redirect online traffic to the illegitimate site instead. While individuals can fix the issue by clearing their device’s cache, shared network caches can quickly re-poison that device and other network devices.

So how do you know if you’ve been targeted by a DNS poisoning attack? Let’s look at the signs.

What Are the Signs of DNS Poisoning?

It’s not easy to tell if you’ve been a victim of DNS poisoning or DNS spoofing, but it’s important to stay vigilant. Here are signs to watch for:

1. Unexpected redirects: Check that the URL of the site you reach matches the URL you entered, and that the page design and interface are what you expect. Any changes in URL characters or top-level domain (e.g., .com or .org), as well as unfamiliar page design elements (especially login interfaces), may indicate DNS poisoning.
2. Slow load times: When web pages take an unusually long time to load, someone may have intercepted your DNS request. Of course, there are many other reasons for slow load times, so this alone can’t verify a DNS attack.
3. Suspicious content (even on a familiar URL): DNS spoofing works by sending users to the wrong IP address — but the URL in your browser’s address bar typically matches the site you intended to visit. If you notice strange or unexpected content, misspellings and other typos, or other types of errors, you could be on a spoofed site.
4. Unusual ads and popups: Some sites are always full of ads and popups. But if a trusted site that’s typically ad-free shows a wealth of unexpected ads, you may be on a malicious website.
5. SSL/TLS certificate warnings: Browsers verify websites through Secure Sockets Layer/Transport Layer Security certificates (commonly called SSL certificates); if the certificate of the site you’re on doesn’t match the real site’s certificate, you may get a browser warning.
6. Suspicious network traffic: A sudden increase in DNS requests, or unexpected requests, could indicate DNS spoofing.

If you suspect DNS spoofing, stop using the suspicious site(s) and check your network settings immediately.

Best Practices to Prevent DNS Poisoning Attacks

Recognizing the potential risk DNS poisoning poses to internet users and organizations alike, it is essential to employ the best practices to mitigate these threats. Here are some ways to strengthen your defenses:

Monitor DNS Activity Closely

Constantly monitoring DNS activity allows for the detection of any suspicious entries in real-time. Using DNS spoofing detection mechanisms can help spot potential security threats before they become a problem. If abnormal traffic patterns or unrecognizable DNS responses are detected, it could indicate a DNS poisoning attempt.

Flush DNS Cache Frequently

DNS cache poisoning thrives on cached data. Both network administrators and individuals should flush network and devicecache data routinely, since this flushes out any stored IP addresses that may be fraudulent. It also requires the DNS resolver to request fresh records.

Update DNS Software Regularly

Make it a habit to keep your DNS server software and operating systems updated. With each update, software developers improve security measures and patch known vulnerabilities that attackers might exploit.

Operate Your Own DNS Server

Running your own DNS server allows for better control over DNS requests and responses, thereby reducing the risk of DNS poisoning attacks. Having your own servers essentially ensures that DNS requests aren’t sent to compromised external DNS servers.

Use Private DNS Servers

A private DNS server only allows DNS requests from recognized and trusted sources, minimizing exposure to potential threats. Restricting who can make DNS requests to your server is another effectivemeasure against DNS poisoning.

Protect Your Network

Use strong network authentication protocols such as 802.1X, which uses digital certificates for mutual authentication of both the client and the server. Protocols such as 802.1x can stop malicious attackers before they gain network access.

Encrypt Data and Communications

Unencrypted connections are vulnerable. But if an attacker infiltrates an encrypted DNS request, they may not be able to manipulate it. Instead of connectionless UDP ports, encrypt traffic with DNS over HTTPS (DoH) or DNS over TLS (DoT) to protect your data and devices.

Use Virtual Private Networks (VPNs)

VPNs provide an additionallayer of security by encrypting communications between your device and the DNS server. This encryption makes it harder for attackers to intercept and change DNS data, thus significantlyreducing the risk of DNS poisoning attacks.

Train End Users

Network administrators shouldn’t be the onlyones who understand the definition, dangers of and prevention methods for DNS spoofing. When you invest in training for all users, it’s easier for them to spot the signs, detect phishing attacks and protect your network and organization.

Implement DNS Security Extensions (DNSSEC)

Domain Name System Security Extensions (DNSSEC) add a layer of authentication to the DNS lookup process, verifying data origin and confirming that the DNS response hasn’t been compromised. By ensuring the authenticity of the DNS data, DNSSEC goes a long way in preventing DNS spoofing attacks. IETF introduced DNSSEC in 2005, but due to a mix of concerns about complexity and return-on-investment (ROI), it still hasn’t been widely adopted.

Implement Passwordless Security

One way to prevent credential theft from a DNS poisoning attack is to simply eliminate the use of credentials. Digital certificates, which are issued and managed by a Public Key Infrastructure (PKI), cannot be stolen or used by other devices. End-users can log into cloud applications, the wired or wireless network or even a VPN using a digital certificate instead of a password.

How Can SecureW2 Protect Your Organization From DNS Poisoning Attacks?

SecureW2 offers robust and cost-effective solutions that protect against DNS poisoning attacks without the complexity of configuring DNS servers in-house. JoinNow Dynamic PKI provides powerful end-to-end encryption, substantially reducing the risk of DNS spoofing attacks by using certificate-driven authentication instead of credentials. 

Our JoinNow Suite ensures that devices are securelyonboarded onto the network with correctly configured settings. This reduces the possibility of connecting to fake or insecure networks, thus mitigating the risk of DNS cache poisoning. 

In a nutshell, SecureW2 offers a comprehensivesecuritysuite for organizations, providing effective defenses against DNS poisoning attacks. By implementing SecureW2 solutions, organizations can ensure a more secure network, protecting both their data and their users from potential cyberattacks.

SecureW2 is not just about safeguarding your present; it’s about securing your future. Schedule a demo to learn how we can protect your organization.