Knowledgebase

introduction

DNS poisoning, also known as DNS cache hijacking or DNS cache poisoning, is a network security threat. DNS (Domain Name System) is a distributed system used on the Internet to convert domain names into IP addresses, similar to a phone book on the Internet, providing users with an easier-to-remember way to access network resources. However, DNS poisoning can disrupt the normal operation of this system, causing users to be mistakenly directed to malicious or unsafe websites.

Definition of DNS Poisoning

DNS pollution refers to malicious attackers tampering with the results of DNS resolution when users visit websites, directing users to wrong websites or preventing them from accessing target websites. Specifically, when a user enters a URL in a browser, the browser will request the local DNS server to resolve the domain name. If the DNS system is polluted, attackers may tamper with the DNS response and redirect users to malicious or phishing websites, resulting in information leakage, phishing attacks, or access to harmful content.

How DNS pollution works

The basic principle of DNS pollution is to tamper with the response of DNS query. Attackers modify DNS response and guide users to fake IP addresses through man-in-the-middle attacks, DNS spoofing, DNS poisoning and other means. Since the DNS system is a distributed system, many nodes (including local DNS servers and root DNS servers) may become attack targets, so attackers can insert false information in multiple links.

Causes of DNS Poisoning

1. Man-in-the-middle attack : The attacker inserts false data between the user and the DNS server to tamper with the DNS response.
2. DNS spoofing : An attacker can trick a DNS server into delivering a false IP address to a user by forging a DNS response.
3. DNS poisoning : An attacker injects false data into the DNS cache, causing subsequent DNS queries to return incorrect results.
4. Improper operation and management : The security of the DNS system depends on the operation level of the node operators and maintenance personnel. Careless operation or improper management can also lead to DNS pollution.

The impact of DNS pollution

1. Privacy and security threats : DNS pollution can redirect users to phishing sites, leading to the theft of sensitive information such as usernames, passwords, and financial information.
2. Internet censorship : Governments in some countries or regions use DNS pollution technology to prevent users from accessing specific websites or services, thereby achieving Internet censorship.
3. Internet segmentation : DNS pollution undermines the global interconnection principle of the Internet, causing users in different regions to receive completely different content when accessing the same domain name, affecting the global sharing of information.

Measures to deal with DNS pollution

1. Change the domain name resolution server : Using a reliable public DNS service, such as Google DNS (8.8.8.8 and 8.8.4.4) or Cloudflare DNS (1.1.1.1), can improve the security of DNS resolution.
2. Clear DNS cache : Clear the local DNS cache regularly to prevent incorrect DNS resolution results from being stored in the cache.
3. Use a VPN or proxy : Encrypt DNS queries through a VPN or proxy service to bypass interference from network operators and enhance network security.
4. Modify the hosts file : Add the mapping relationship of the polluted domain name to the hosts file in the operating system to directly solve the DNS pollution problem.
5. Enable HTTPS : Use HTTPS to encrypt the connection, increase the security of data transmission, and reduce the risk of man-in-the-middle attacks.
6. Change the domain name : If the pollution is serious and difficult to repair, you can consider changing the domain name and redirect the traffic of the old domain name 301 to the new domain name.

Summarize

DNS pollution is a serious network threat that may lead to user privacy leakage and information security issues, and also poses a threat to the freedom and security of the Internet. In order to combat DNS pollution, users, network operators and governments need to work together to maintain an open and secure Internet environment by raising security awareness, adopting advanced technologies and implementing effective protection measures.