What Is DNS Spoofing (DNS Cache Poisoning) and How Do You Prevent it?
DNS (Domain Name System) plays a critical role in how we navigate the internet, but it’s also a prime target for attackers. In fact, a staggering 90% of organizations—especially high-risk industries like finance, government, healthcare, and media—suffer from DNS attacks.
One of the most prevalent forms of these attacks is DNS cache poisoning, also known as DNS cache spoofing or, most commonly, DNS spoofing.
In this article, we’ll discuss what DNS spoofing entails and, more importantly, how you can safeguard your organization against it.
What is DNS, and what is a DNS server?
To better understand DNS spoofing it’s essential to know the basics of DNS and DNS servers first.
The Domain Name System (DNS) is the phonebook of the internet. It translates human-readable domain names, like Domain.com, into IP addresses, such as 192.0.2.1, which computers use to communicate.
A DNS server, on the other hand, is a specialized server within the domain name system. It’s responsible for translating domain names into IP addresses. There are four DNS servers involved in loading a web page.
- DNS resolver
- Root nameserver
- TLD nameserver
- Authoritative nameserver
Each of these servers work together to ensure that when you type in a domain name into the browser, you reach the correct website efficiently. Understanding this system is key to recognizing how attacks like DNS cache poisoning can disrupt our online experience.
What is DNS spoofing?
DNS spoofing is a type of cyber-attack where attackers insert false information into the DNS resolver and corrupt the cached information. This way, cybercriminals can manipulate the resolver and redirect users to malicious websites.
To understand DNS spoofing better, it’s important to understand what the attackers are aiming to poison—the DNS cache.
DNS caching is the process of storing DNS query results on a local device or DNS server. This process speeds up internet browsing.
When you visit a website, your device queries DNS servers to locate the IP address. To avoid repeating the same lookup process all the time, the DNS resolver stores the IP address queries temporarily. This way, when you revisit a website, your device can easily pull the IP address directly from the cache.
How does DNS cache poisoning work?
Attackers poison a DNS cache by impersonating DNS nameservers. This way, they can reply to a query from a DNS resolver with a malicious IP address.
The domain name system uses User Datagram Protocol for all DNS queries and responses. The user datagram protocol (UDP) is a communication protocol that does not require prior communication to set up communication paths. For this reason, attackers can easily pretend to give legitimate responses to the DNS resolver.
Additionally, a DNS resolver can unknowingly accept and cache the wrong IP address since there’s no way to verify if a response is coming from a legitimate server.
To fully understand how attackers orchestrate a DNS poisoning, here’s a detailed scenario.
- Set up. A malicious actor spots the vulnerabilities of a DNS server. They determine whether a DNS server uses DNS encryption or Domain Name System Security Extensions (DNSSEC).
- Modifying MAC address. The attacker modifies their Media Access Control (MAC) address to impersonate a DNS server. This way, the attacker can blend in with the network, making it easier to manipulate web traffic without suspicion.
- IP packet forwarding. The attacker then intercepts DNS requests by forwarding IP packets to a corrupted DNS server. This process allows the attacker to control the flow of DNS traffic, hijacking DNS requests to redirect users to a cybercriminal’s server.
- Creating the host file. The host file is a local file in a user’s device that maps domain names to IP addresses without going through the entire DNS. Attackers add corrupted entries in this file to redirect users to their sites without affecting external DNS servers.
- Creating a fake website. Attackers often create a fake website that resembles the legitimate site users expect to land on. This way, they can capture sensitive data.
- Redirecting the DNS request. Attackers redirect DNS requests to their local host files using a DNS spoofing tool.
- Displaying the fake website. Now, users land on fake websites where they can unknowingly share their personal information, such as usernames, passwords, and card numbers.
Types of DNS cache poisoning or DNS spoofing attacks
DNS cache poisoning and spoofing come in various forms. Here are some of the most common types of DNS spoofing attacks.
Man Man-in-the-Middle (MITM) Attacks
A Man-in-the-Middle (MITM) attack involves intercepting and altering DNS communication between a user and the DNS servers. Attackers position themselves between the user and the DNS resolver to receive and modify DNS queries in real-time.
DNS Server Compromise
In this type of attack, cybercriminals take over the DNS resolution process by manipulating responses to redirect users to a malicious website. They hijack and configure a DNS server to respond with malicious IP addresses.
Exploiting Time-To-Live (TTL)
A user’s device stores data for specific periods to speed up access. Hackers can take advantage of this by manipulating the Time-to-Live (TTL) value of the DNS server cache. By adjusting the TTL, an attacker manipulates the TTL value to ensure the servers store incorrect responses for extended periods.
Consequences of DNS spoofing attacks
DNS cache poisoning can have serious consequences that impact an individual, a business, and even an entire nation. Here’s a closer look at the risks associated with DNS poisoning attacks.
Data theft
Attackers can trick users into thinking that they’re navigating through legitimate websites. So, when a user attempts to enter their login credentials or personal data, attackers capture the information and use it for identity theft, fraud, and unauthorized account access.
Malware infection
Attracting a user to a malicious site can automatically download malware into their device, such as ransomware and spyware. This allows attackers to monitor user activities and spread malware to connected devices.
Censorship
Some countries purposefully poison users’ DNS caches. The government authorities do this to censor or block access to certain websites, especially websites with adult content. The government also uses DNS poisoning to block the nation’s access to social media and media outlets.
Prevented security updates
Outdated software is an easy entry point for cyberattacks. For this reason, attackers use DNS cache poisoning to redirect devices to fake update servers. When a device attempts to download a security or software update, it receives a malicious version of the system update.
Attackers can also block a system or device from updating. Attackers use this tactic, especially in corporate or government networks.
How to protect your DNS
The DNS can be vulnerable to cyberattacks. Fortunately, there are a few extra steps you can take to prevent DNS poisoning.
For website owners
Integrate DNSSEC
The DNSSEC or DNS security extensions add an extra layer of security to the DNS by using digital signatures to verify whether the DNS data it receives is tampered with. This ensures that the user’s DNS queries receive accurate information.
Incorporate SSL certificates
Domain.com’s SSL certificates encrypt sensitive data. This way, attackers can’t intercept or acquire important data during the transfer process.
An SSL certificate also provides credibility to websites. Domain.com’s SSL certificate includes a graphic seal indicating that your website is secure.
Use DNS spoofing detection tools
DNS spoofing detection tools monitor DNS traffic. It detects suspicious activities and potential cache poisoning attempts.
These tools can identify unexpected changes in the DNS, alerting website owners of the DNS activities.
For endpoint users
Avoid unrecognizable links
Be cautious with unfamiliar links, especially if it comes from an email or messaging app. Hackers often use these communication channels since connecting directly to the target is more accessible.
To stay safe, hover over links to see the actual URL and before clicking.
Scan your device regularly
Regular scanning of your device is an effective way to prevent attackers from making further attacks. Use reliable antivirus and anti-malware software to help detect and remove malicious software within a device.
Additionally, regularly updating antivirus software further ensures protection against newer threats.
Delete cache
Regular cleaning of your DNS cache can reduce the risk of accidentally using a poisoned IP address. By flushing the DNS cache, you’re forcing the DNS resolver to look up fresh DNS information.
Use a VPN
A virtual private network (VPN) is one way to encrypt data exchange over the internet. VPN also encrypts DNS queries, making it hard for attackers to intercept with the DNS resolution process.
VPNs also use their own secure DNS servers. This adds another layer of protection against cyber-attacks like DNS spoofing.
Make sure a website is secure
Before entering personal information, such as your name, address, and card number, onto a website, check if it’s secure. How? Here are indicators of a secure website.
- The URL uses https instead of http.
- It has a padlock icon next to the URL
Safeguard your internet journey with Domain.com
DNS cache poisoning is a serious threat with serious consequences. It impacts individual users, businesses, and organizations on a large scale. Taking steps to secure DNS is crucial, especially for website owners, to ensure a credible and safe space for their web visitors.
Domain.com provides a range of security tools, like SSL certificates and SiteLock, making it easier to protect your website and visitors from malicious attacks.
Frequently asked questions
Symptoms of DNS cache poisoning involve unexpected redirection to unfamiliar websites, security warnings on trusted sites, slow loading time, and unusual pop-ups.
No, clearing the DNS cache will only delete the temporary database of web address translations, not your browsing history.
Clearing the DNS cache will flush all IP addresses and DNS records in your cache. So, when opening a website, your browser and the resolver will have to make a DNS request for that website again.
Disabling DNS caching slows the process of opening a website since your local host file won’t have any previous record of any website to rely on.
An IP packet is the data used to transmit data across computer networks. It contains two main sections: the Header, which consists of information like IP version, source IP address, and TTL, and the Payload, which holds the actual data transmitted, such as a website request or email content.
