What is DNS cache poisoning and how does it affect security?

26 September 2024 4 minutes Author: Cyber Witcher

DNS cache poisoning is a cyber threat that allows attackers to spoof DNS queries to redirect users to malicious sites. Learn how this attack works, how to detect it and protect yourself from potential threats.

What is DNS cache poisoning?

DNS cache poisoning, also known as DNS spoofing, is a type of cyberattack in which users trying to access a legitimate website are redirected to another, usually malicious, website. When a user enters a site address in a browser, DNS servers assign the corresponding IP address to load the page. Attackers, by modifying or replacing information in the DNS cache, can direct users to fake or dangerous sites in order to steal their data or accounts.

What is DNS?

DNS translates human-readable website addresses, such as example.com, into machine-readable IP addresses. This allows users to easily navigate the web without having to remember complex numerical sequences for each site.

The DNS system uses different types of name servers. Authoritative name servers maintain the official records for specific domains, while recursive DNS servers or resolvers receive requests from users and, if necessary, contact authoritative servers for information.

What is DNS caching and how does cache poisoning work?

DNS servers use caching to speed up responses by storing information from previous queries. This allows for faster data retrieval during subsequent accesses to the same resources. A DNS cache poisoning attack occurs when attackers replace legitimate DNS cache entries with spoofed addresses. As a result, when a user tries to access a legitimate site, the DNS server returns a fake IP address, redirecting the user to a malicious site.

How do attackers poison the cache?

Hackers can directly hijack a DNS server or use malware to change the browser’s DNS cache when a user clicks on malicious links. A man-in-the-middle attack is also possible, where attackers place themselves between the browser and the DNS server, redirecting requests to malicious resources.

DNS cache poisoning is most commonly used for phishing attacks. By creating fake sites that look like real ones, hackers obtain user credentials, allowing them to steal money or use the information for other attacks.

Why are cache poisoning attacks so effective?

DNS was created to handle queries precisely and does not provide verification of their intent, so it is a vulnerable protocol. In addition, DNS traffic often passes through firewalls without additional validation, making it an attractive vector for hacker attacks.

What is cache poisoning and DNS spoofing?

Although the terms “DNS cache poisoning” and “spoofing” are often used interchangeably, they are sometimes distinguished. Cache poisoning is an attack method that results in spoofing, i.e. forging DNS records.

Signs of an attack include a sudden drop in traffic or abnormal DNS activity on the domain. Detecting DNS cache poisoning on your own is difficult, so the best solution is to use automated DNS security monitoring tools.

How can I prevent DNS cache poisoning?

Organizations can prevent DNS poisoning by following several cybersecurity best practices.

  • Accept DNSSEC. Domain Name System Security Extensions (DNSSEC) offer a way to verify the integrity of DNS data. DNSSEC uses public key cryptography to verify and authenticate data.

  • Update and patch your DNS software regularly. Establishing an optimal frequency for updating and patching DNS programs reduces the likelihood that attackers will exploit known or zero-day vulnerabilities.

  • Use HTTPS for DNS traffic. DNS over HTTPS (DoH) encrypts DNS traffic by passing queries through an encrypted HTTPS session to improve privacy and hide DNS queries.

  • Use a Zero Trust approach when configuring DNS servers. Zero trust principles require that all users, devices, applications, and requests be considered compromised unless they are authenticated and continuously validated. DNS is a valuable zero-trust checkpoint where every Internet address can be scanned for potentially malicious behavior.

  • Choose a fast and DoS-resistant DNS resolver. Cache poisoning attacks depend on the latency of DNS server responses, so a fast resolver can help prevent successful attacks. A DNS resolver should also have cache poisoning controls built in. Major ISPs and DNS providers have the scale to overcome DDoS attacks.

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