With the continuous escalation of cyberattacks, DNS pollution and DNS hijacking have become two common problems that impact online experience and data security. For companies operating websites or applications, preventing both DNS pollution and hijacking at the server level has become a core task for improving service quality and ensuring stable user access.

　　DNS, standing for Domain Name System, is a critical piece of internet infrastructure. It resolves user-entered domain names into corresponding IP addresses, enabling browsers and applications to locate the target server. Because DNS performs this crucial navigation function, if it is polluted or hijacked, users may be directed to the wrong server, resulting in inaccessible pages, abnormal web pages, and even data leaks.

　　DNS pollution occurs when hackers or third parties inject false records into caches or resolution processes, causing users to receive incorrect resolution results. DNS hijacking is more direct, often occurring at local network operators or malicious nodes. Attackers intercept user requests and return forged results, redirecting users to malicious websites. While these two attack methods differ, both can result in users being unable to access their target website or being directed to a fake one, potentially leaking sensitive information.

　　To prevent DNS pollution and hijacking on the server side, multi-layered protection measures are necessary:

　　First, deploy a secure and reliable DNS resolution service. In most cases, websites and applications use authoritative DNS servers for domain name resolution, so the security of authoritative DNS is paramount. Choosing a DNS service provider with globally distributed nodes and robust protection capabilities can effectively reduce the risk of pollution and hijacking. Especially in cross-border access scenarios, distributed nodes ensure that resolution requests are routed through the closest trusted channel, minimizing the risk of tampering.

　　Second, the server itself can also be configured to enhance protection. Enabling DNSSEC (Domain Name System Security Extensions) is the most common and effective measure. DNSSEC adds a digital signature mechanism to the existing DNS protocol, verifying the authenticity and integrity of DNS records. When users or recursive resolvers receive resolution results, they can verify the signatures to confirm that the result is authoritative and has not been tampered with. If a forged record is detected, the resolver will directly reject the request, effectively preventing pollution and hijacking. While deploying DNSSEC requires certain server performance requirements, it fundamentally improves the credibility of the DNS and is a widely recommended standard practice in the industry.

　　Server operators can also incorporate encryption protocols into their network architecture. Traditional DNS queries are transmitted in clear text, making them vulnerable to interception or tampering. The recently emerged DoT and DoH protocols encrypt DNS queries, preventing third parties from inserting malicious data during transmission. Servers can mandate the use of encrypted DNS on clients or prioritize resolvers that support encryption during their own resolutions, thereby reducing the risk of hijacking.

　　In addition to protocol-level protection, the proper use of CDNs is also an effective measure. CDN providers typically possess robust node networks and security capabilities, acting as an intermediary between users and origin servers. CDN nodes can absorb large volumes of requests and intelligently schedule them, reducing the risk of single points of attack. Furthermore, CDN DNS systems often have built-in anti-hijacking and anti-pollution mechanisms, helping servers mitigate many common network attack scenarios. For businesses serving global users, integrating a CDN not only optimizes access speeds but also enhances DNS security.

　　In terms of server protection, operations personnel should also focus on ensuring the appropriateness of local configurations. For example, prohibit unauthorized recursive queries to prevent servers from being used as amplification attack tools; regularly update systems and DNS software to patch known vulnerabilities; and use firewall rules to limit unnecessary port openings to reduce attack vectors. Furthermore, enable log auditing to monitor DNS queries and server access in real time. Any surge in unusual requests or abnormal resolution results should be immediately investigated and emergency measures implemented.

　　In some special scenarios, reliability can be enhanced through multiple routes and intelligent scheduling. Even if a route is contaminated or hijacked, the system can automatically switch to a backup route, ensuring that users can still access the correct server. Large enterprises often deploy multiple authoritative DNS servers, distributed across different regions and carrier environments, to mitigate the risk of single points of failure or regional hijacking.

　　In addition to technical measures, server operators must also prioritize security awareness. DNS contamination and hijacking are often not isolated attacks, but are often combined with phishing, traffic hijacking, ad injection, and other attacks. Lack of security awareness among operations and maintenance personnel can leave vulnerabilities in certificate configuration, key management, access control, and other aspects, creating opportunities for attackers to exploit. Therefore, establishing comprehensive security protocols and emergency response plans is essential for preventing these risks.

　　In the future, with the widespread adoption of DNS encryption and IPv6, DNS security issues will gradually ease. However, at this stage, servers still need to implement multi-layered measures to prevent contamination and hijacking. Whether choosing a reliable DNS service provider, enabling DNSSEC and encryption protocols, or integrating CDN and multi-connection architecture, the ultimate goal is to ensure that users can accurately access the target server after entering a domain name. This is crucial not only for website availability but also for user data security and trust.