DNS poisoning is a cyberattack targeting the domain name resolution system. By tampering with DNS response packets, users are redirected to incorrect IP addresses. This phenomenon not only impacts the online experience but can also lead to security risks such as information leakage and phishing. Effectively combating DNS poisoning requires a comprehensive technical framework, from detection to prevention.

Identifying DNS poisoning is the first step in resolving the issue. Comparing the resolution results of multiple authoritative DNS servers can provide a preliminary assessment of whether poisoning exists. Using command-line tools to compare multiple server queries is an effective method. If different DNS servers display significant discrepancies in their resolution results for the same domain name, particularly if they return clearly incorrect IP addresses (such as private addresses or non-existent public addresses), DNS poisoning is highly likely. Further packet analysis can help identify the characteristics of poisoning. By capturing DNS query and response packets, analyzing abnormal TTL values, source ports, and response speeds, these are often characteristic indicators of DNS poisoning. Online detection tools can also provide additional verification, but it is important to select a trusted detection platform.

Deploying an encrypted DNS protocol is a core technical measure to prevent poisoning. DNS-over-HTTPS (DoH) and DNS-over-TLS (DoT) effectively prevent man-in-the-middle tampering by encrypting DNS queries and responses. At the client level, modern major browsers support the DoH protocol and can be enabled through configuration. System-wide configuration requires specifying the DoT server address and enforcing TLS encryption in network settings. Technical users can deploy a local DNS encryption proxy service to forward all DNS queries to a trusted recursive resolver through an encrypted tunnel. Enterprise environments can consider deploying a dedicated DNS security gateway to centrally manage all DNS queries and provide encryption protection.

For users who host their own DNS servers, additional security hardening measures are necessary. DNSSEC (Domain Name System Security Extensions) verifies the authenticity of DNS data through digital signatures, effectively preventing data tampering. Deploying DNSSEC requires configuring keys on the authoritative server and signing zone data, as well as enabling verification on the recursive resolver. Response Policy Zones (RPZ) allow administrators to customize filtering rules to proactively block known malicious domains or suspected poisoning. A DNS firewall solution can also be considered to detect and block anomalous query patterns in real time.

Implementing network-level protections can enhance overall security. Configure firewall rules to block suspicious DNS response packets, especially those containing private or reserved addresses. Enforcing the use of TCP for DNS queries can improve resilience, as TCP connections are more difficult to hijack than UDP. Enterprise networks can consider deploying dedicated DNS proxy devices to forward all DNS queries and implement security checks at the proxy layer.

Establishing a comprehensive monitoring system is key to promptly detecting and addressing DNS pollution. Deploy real-time DNS traffic monitoring tools to detect abnormal query patterns and response characteristics. Set up automated detection scripts to regularly verify the accuracy of resolution results for important domain names. Develop an emergency response plan that clearly defines the procedures to be taken upon discovery of DNS pollution, including switching DNS servers, clearing local caches, and notifying affected users. Maintain detailed DNS query logs for post-incident analysis and forensics.

The most effective protection strategy is a multi-layered, defense-in-depth strategy. Configure encrypted DNS settings on endpoints to ensure the security of outbound queries. Deploy DNS filtering devices at the network perimeter to detect and block malicious responses. Deploy security extensions on servers to verify the authenticity of DNS data. Establish a regular audit mechanism to evaluate the effectiveness of protective measures and adjust them promptly.

DNS security protection is an ongoing process. DNS software should be regularly updated to patch known vulnerabilities. Keep up-to-date on the latest DNS security threat intelligence and adjust protection strategies promptly. Network administrators should receive professional training to enhance their ability to identify and handle DNS security incidents. Establish communication channels with ISPs or DNS service providers to enable rapid coordination and response in the event of large-scale DNS pollution.

Systematically implementing the above solutions can significantly enhance your network's resilience to DNS pollution. It's important to note that no single solution can provide complete protection; a comprehensive approach requires the integration of multiple technologies to build a reliable DNS security system. In actual deployment, the most appropriate combination of technologies should be selected based on the specific network environment and business needs, and a comprehensive monitoring and emergency response mechanism should be established.