DNS Cache Poisoning

Definition of DNS Cache Poisoning

DNS Cache Poisoning, also known as DNS spoofing, is a cyber attack technique in which an attacker corrupts or manipulates a Domain Name System (DNS) cache. This leads to the redirection of users to malicious or undesired websites when they attempt to access a legitimate domain. The goal is often to steal sensitive information or spread malware by tricking users into believing they are visiting a trusted site.


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Key Takeaways

  1. DNS Cache Poisoning is a type of cyber attack that exploits vulnerabilities in the DNS system to redirect users to malicious websites, potentially gaining access to sensitive information.
  2. To protect against DNS Cache Poisoning, it is essential to implement security measures such as using DNSSEC, which provides additional authentication and validation for DNS responses, and keeping software up to date with the latest patches and security updates.
  3. Monitoring DNS traffic for unusual patterns or malicious activities may also help in detecting DNS Cache Poisoning attacks, enabling organizations to respond promptly and effectively to mitigate potential damage.

Importance of DNS Cache Poisoning

DNS Cache Poisoning is an important term in technology because it represents a critical security risk within the Domain Name System (DNS) that can potentially compromise the integrity and reliability of information on the internet.

The attack involves a malicious actor corrupting a DNS server’s cache by inserting fraudulent IP addresses corresponding to a target domain, ultimately redirecting users to rogue websites or interrupting access to legitimate sites.

This can lead to serious consequences such as theft of sensitive information, distribution of malware, and large-scale network disruption.

Understanding and addressing DNS Cache Poisoning is crucial to maintaining a safe and secure online environment for users and businesses alike.


DNS Cache Poisoning, also known as DNS spoofing, is a cyber attack technique used by malicious individuals or groups to exploit vulnerabilities in the Domain Name System (DNS). The primary purpose of this attack is to redirect internet traffic to fraudulent websites or servers without the user’s knowledge or consent. This type of attack alters the DNS resolver cache, causing it to resolve domain names to incorrect IP addresses. By doing so, the attacker can manipulate web traffic, steal sensitive information, or even spread malware.

Thus, DNS Cache Poisoning is a significant concern for both individuals and organizations as it threatens the integrity and security of their digital assets. To accomplish DNS Cache Poisoning, attackers send fake DNS responses to the targeted DNS resolver, which impersonates legitimate responses. Once the fake response is accepted, the compromised DNS cache information is then used to route unsuspecting users to rogue websites and servers.

Web browsers typically trust the DNS resolver to provide accurate information, so users may remain unaware that they are being directed to malicious sites. To protect against DNS Cache Poisoning, organizations employ a variety of security measures, including using DNS Security Extensions (DNSSEC), which cryptographically verifies DNS data to ensure its authenticity. Additionally, regularly updating and patching DNS software can help mitigate the risk of exploiting vulnerabilities that may lead to DNS Cache Poisoning.

Examples of DNS Cache Poisoning

DNS Cache Poisoning is a cyberattack technique that exploits vulnerabilities in the Domain Name System (DNS) to redirect internet traffic to malicious websites. Here are three real-world examples of such attacks:

Kaminsky DNS Vulnerability (2008):In July 2008, security researcher Dan Kaminsky identified a significant flaw in the DNS protocol that allowed attackers to easily execute cache poisoning attacks. This vulnerability affected almost all DNS software implementations, and if exploited, attackers could redirect users to malicious websites, intercept emails, and cause other disruptive activities. Once the flaw was disclosed, software vendors released patches to mitigate the risk, and many internet service providers updated their DNS servers to prevent possible attacks. This example led to extensive media coverage and raised awareness about the need to secure DNS infrastructure.

Brazilian ISPs DNS Poisoning Attack (2011):In 2011, several Brazilian ISPs were targeted in a widespread DNS cache poisoning attack. Cybercriminals exploited the ISPs’ DNS servers to redirect users attempting to visit popular websites like Google, YouTube, and Hotmail to malicious websites that served banking Trojans. These Trojans aimed to steal users’ banking credentials, leading to financial losses for the affected individuals. This attack highlighted the importance of securing DNS servers to protect users from fraudulent activities.

The Great Cannon Attack (2015):In 2015, a large-scale cyberattack dubbed “The Great Cannon” was discovered, which targeted the Chinese software development platform GitHub. Researchers believe that this attack was orchestrated by the Chinese government to censor web content and suppress online dissent. The attackers employed a DNS cache poisoning technique to hijack web traffic from Chinese search engine Baidu and redirect it towards GitHub, causing a massive Distributed Denial of Service (DDoS) attack. The DDoS attack knocked GitHub offline, affecting numerous software projects hosted on the platform. As a result, the Great Cannon attack illustrated how DNS cache poisoning can be weaponized by nation-states to disrupt internet services and enforce cyber censorship.

FAQ: DNS Cache Poisoning

What is DNS Cache Poisoning?

DNS Cache Poisoning is a cyber attack where an attacker corrupts a DNS server’s cache by injecting false DNS information. This results in users being redirected to malicious websites instead of the intended legitimate ones.

How does DNS Cache Poisoning work?

The attacker exploits vulnerabilities in the DNS system by sending falsified DNS responses to a target DNS server, pretending to be from an authoritative server. When the target server receives these responses, it caches them and forwards them to users.

What are the consequences of DNS Cache Poisoning?

The consequences include having users unknowingly visit malicious sites or being redirected to phishing pages, which can lead to identity theft, malware infections, and other security breaches.

How can DNS Cache Poisoning be prevented?

Prevention methods include using DNSSEC (Domain Name System Security Extensions) to verify the authenticity of responses, implementing Source IP Address validation, using a random query ID, and frequently updating and patching DNS software to address vulnerabilities.

How can I check if my DNS cache has been poisoned?

You can check by comparing the DNS records stored in your cache with the authoritative server’s records. If there’s a discrepancy, it could potentially be an indicator of cache poisoning. You can use online DNS lookup tools and check your local DNS cache entries to inspect for suspicious entries.

Related Technology Terms

  • DNS Spoofing
  • Domain Name System Security Extensions (DNSSEC)
  • Resolver
  • Time-to-Live (TTL)
  • Recursive Query

Sources for More Information


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