DNS Poisoning & DNS Spoofing: Meaning, Definition, and How These Attacks Work

You type “paypal.com” into your web browser, but instead of landing on the real site, you’re redirected to a clone that steals your password. This isn’t magic—it’s DNS poisoning (aka DNS spoofing), where hackers mess with the internet’s “phonebook” to send you to malicious sites.

Here’s the kicker: every website you visit relies on the Domain Name System (DNS) to translate “google.com” into an IP address. But if attackers poison a DNS cache—think of it as slipping fake entries into the phonebook—they can reroute you wherever they want. Worse, DNS server responses aren’t always checked for integrity of DNS data, making it easy to inject false information in a DNS resolver.

For example, when authoritative DNS servers (the official source for DNS records) get bypassed, recursive DNS resolvers (your device’s “librarian”) might unknowingly store fake DNS information. This cache poisoning vs spoofing mess is why attacks like the 2021 major DNS breach in Europe redirected thousands to phishing pages.

But here’s the good news: Domain Name System Security Extensions (DNSSEC) and tools like DNS over HTTPS are fighting back. Want to learn how to prevent these attacks? Let’s break down how DNS poisoning and spoofing work—and how to slam the brakes on hackers.

What is DNS Poisoning?

DNS poisoning (or DNS cache poisoning) is when hackers slip fake DNS information into a resolver’s cache—like swapping road signs to reroute traffic. When you visit a site, your device asks a DNS resolver for the correct IP address. If attackers poison the cache, the resolver stores fake addresses, sending you to phishing sites or malware hubs.

This isn’t rare: the DNS infrastructure wasn’t built to stop these tricks. For example, DNS resolvers store addresses for speed, but without verifying DNS data, hackers exploit DNS queries to sneak in malicious entries. A fast, DoS-resistant resolver can spread these successful attacks to thousands.

To fight back, use secure DNS protocols and automated DNS monitoring to catch shady DNS activity.

How DNS Poisoning Works

Imagine you’re looking up a website using DNS like checking a phonebook. Normally, the DNS resolver returns the correct IP address from its cache. But in a DNS poisoning attack, hackers sneak in fake entries—essentially, they poison the DNS cache with false information. This method, which falls under poisoning and DNS spoofing, exploits minor changes in DNS queries since the DNS system wasn’t built with robust security. Even a fast and DoS-resistant DNS resolver can be tricked into providing an incorrect address in its cache.

Essentially, cache poisoning is the act of injecting false DNS data, and it poses significant risks. By learning how DNS poisoning and DNS spoofing work, you can take steps to help prevent DNS poisoning and secure your DNS infrastructure.

Key Mechanisms of DNS Poisoning

• Manipulation of DNS queries and DNS responses to inject false DNS data
• Hijacking DNS resolver cache entries to alter domain name system records
• Exploiting vulnerabilities in the DNS protocol to poison the cache

DNS Spoofing vs. DNS Poisoning

While both attacks reroute your traffic, they’re as different as pickpocketing vs. forgery:

• DNS-Poisoning:  Hackers poison a DNS cache (stored in DNS resolvers) with fake entries, tricking the resolver into serving bad addresses. Since DNS was built for speed, not security, attackers exploit how DNS resolvers provide quick answers without always verifying DNS data. For example, a typical DNS resolver handling a high number of DNS queries might cache a poisoned entry, spreading it to all users.
• DNS-Spoofing: Here, attackers send fake DNS responses before the real ones arrive, like forging a return address on a letter. This cache poisoning or DNS spoofing tactic exploits how DNS works—since requests aren’t encrypted, hackers with access to a DNS query can hijack it. This poisoning happens in transit, making it harder to detect than cache poisoning.

Types of DNS Poisoning Attacks

DNS poisoning isn’t a one-trick show—it comes in flavors designed to exploit how DNS works. The two most common? DNS cache poisoning and DNS spoofing. Both reroute your traffic, but they play different games.

DNS Cache Poisoning Attack

This attack is like contaminating a city’s water supply. Hackers poison a DNS cache (stored in resolvers) with fake entries, tricking the DNS resolver into serving bad addresses. Since resolvers depend on cached data for speed, a single poisoned entry can infect thousands. For example, if a resolver is using outdated software, attackers exploit this to hijack future DNS queries.

DNS Spoofing Attack

DNS spoofing (also known as DNS hijacking) is more like forging fake IDs. Attackers intercept DNS queries and send fake responses before the real ones arrive. This works because DNS still relies on unencrypted protocols, making it easy to mimic legitimate servers. The risks posed by DNS spoofing include redirecting users to phishing sites or malware hubs.

The Role of DNS Servers and Resolvers

DNS servers and resolvers are the internet’s translators—they turn “netflix.com” into numbers (IP addresses) your device understands. But if attackers slip fake entries into their cache, they become unwitting accomplices in DNS attacks.

What is a DNS Resolver?

Think of a DNS resolver as your device’s “Google Maps” for the web. When you type a URL, the resolver checks its cache (which depends on stored data) or asks DNS servers for directions. But if the resolver is using a poisoned cache, you’ll end up on a hacker’s detour.

The Function of a DNS Server

• Authoritative DNS Server: The “source of truth” for a domain’s IP address.
• Recursive DNS Server: The “detective” that hunts down answers for your queries.

These servers are prime targets for DNS cache poisoning or DNS spoofing, where attackers inject cache with fake entries to reroute traffic.

How DNS Requests and Responses Work

You type “youtube.com” → your device asks the resolver.
Resolver checks its cache → if empty, asks DNS servers.
Authoritative server responds → resolver stores the IP.

If attackers suggest that poisoning occurred mid-request, you’re redirected to a scam site.

How to Prevent DNS Poisoning

To outsmart DNS poisoning, start by using a secure DNS resolver (like Cloudflare or Google). Regularly flush your DNS cache to wipe out stale or poisoned entries, and keep your DNS software updated to patch vulnerabilities.

DNSSEC: DNS Security Extensions

DNSSEC acts like a “seal of approval” for DNS data. If your DNS resolver is using DNSSEC, it checks digital signatures to ensure responses aren’t tampered with. This stops attackers from sneaking poisoned entries into the cache.

Flushing the DNS Cache and Patching DNS Software

Your cache depends on fresh data—flush it regularly (like clearing your browser history). Pair this with updating DNS software to fix loopholes attackers exploit.

Configuring Your DNS for Security

Switch to DNS providers that offer encryption (like DNS over HTTPS). Disable unused features in your DNS settings to shrink the attack surface.

FAQs