With the development of the internet, network security issues have become increasingly prominent. DNS poisoning and HTTP hijacking are common network attack methods. While they may appear similar, such as causing website access errors or redirecting to error pages, their nature, mechanisms, potential harms, and preventative measures differ significantly. Understanding the differences between the two can help both businesses and individuals improve their network security awareness and implement effective protective measures.
DNS poisoning, also known as DNS spoofing or DNS cache poisoning, occurs when an attacker tamperes with domain name resolution results, redirecting users to incorrect IP addresses when accessing specific websites, ultimately leading to accessing servers controlled by the attacker. The Domain Name System (DNS) is a crucial component of internet infrastructure, resolving user-entered domain names to corresponding server IP addresses. DNS poisoning essentially interferes with this resolution process, distorting the results. For example, a user attempting to access a bank's website might receive an attacker-specified IP address from the DNS server, redirecting them to a fake website, potentially leaking personal account information or downloading malicious programs. Common methods of DNS poisoning include cache poisoning, domain hijacking, and malware modifying local DNS settings. Cache poisoning occurs when an attacker injects incorrect resolution records into a DNS server, redirecting subsequent users to the wrong IP address when accessing the same domain name. Domain hijacking typically occurs at the ISP or network node level, where the attacker directly modifies DNS responses. Malware can hijack traffic by modifying a user's local DNS settings. DNS poisoning is characterized by the attack occurring during the domain name resolution phase, independent of specific protocols. It can affect all domain-based access and is difficult for users to detect.
In contrast, HTTP hijacking occurs when an attacker modifies HTTP requests or responses between a user and a server to illegally control access, insert advertisements, or steal data. HTTP is the fundamental communication protocol for the World Wide Web, responsible for web browsing and data transmission. HTTP hijacking is commonly found on public Wi-Fi networks, routers, or ISP nodes. Attack methods include traffic redirection, content manipulation, and session hijacking. Traffic redirection occurs when a user is forced to redirect to an advertising page or phishing website when accessing a webpage. Content manipulation involves inserting advertisements or malicious code into webpage content, impacting the user experience. Session hijacking intercepts HTTP session information to directly obtain user login status or sensitive information. HTTP hijacking is characterized by attacks occurring at the HTTP request or response stage, typically affecting only HTTP traffic, while HTTPS-encrypted content is less susceptible to tampering. Attacks are often visible, such as abnormal webpage content, increased advertising, or redirects to other pages.
From a technical perspective, DNS pollution and HTTP hijacking operate at different levels. DNS pollution occurs at the domain name resolution layer, typically targeting DNS servers or network nodes. The attack essentially tampers with domain name resolution results, causing users to access incorrect IP addresses. This has a wide impact, potentially affecting any requests to the tainted domain, yet is often difficult to detect directly. HTTP hijacking, on the other hand, occurs at the application layer, affecting HTTP requests and responses. The attack may originate at routers, proxy servers, or ISP nodes. The attack essentially tampers with data between users and servers, typically affecting HTTP traffic. Users may directly see tampered webpages or redirects to abnormal pages. Simply put, DNS pollution affects the "entry point" of access, while HTTP hijacking affects the "content" of access.
DNS pollution and HTTP hijacking each have their own distinct dangers. DNS pollution can prevent users from accessing legitimate websites, impacting their online experience. It also poses a risk of phishing, with users being directed to fake websites that could steal personal information. For businesses, DNS pollution can lead to business disruptions and damage their reputation. Furthermore, since the attack occurs during the resolution phase, tracing the source is difficult. The main dangers of HTTP hijacking include web page defacement, the proliferation of advertisements and misleading pages, the potential interception of user data, and the amplification of security vulnerabilities. HTTP hijacking is particularly vulnerable on public Wi-Fi, where man-in-the-middle attacks can lead to the theft of user account and payment information.
Methods to protect against DNS pollution include using trusted DNS servers, such as Google DNS (8.8.8.8) or Cloudflare DNS (1.1.1.1), and encrypting DNS requests using DNS over HTTPS (DoH) or DNS over TLS (DoT) to prevent tampering during the resolution process. Regularly flushing the DNS cache can mitigate the impact of cache poisoning. For critical domains, static resolution can be configured in the local hosts file to improve access security. Effective protection against HTTP hijacking primarily involves using HTTPS for encrypted access and enabling the HSTS (HTTP Strict Transport Security) policy to force browsers to use HTTPS, preventing content tampering. Additionally, avoiding untrusted public Wi-Fi or using to encrypt traffic can reduce the risk of HTTP hijacking. Updating browser and router firmware to patch known vulnerabilities is also a crucial safeguard.
In real-world cases, DNS poisoning has caused some users to be unable to access search engines or banking websites. Packet capture analysis revealed that DNS resolution results were tampered with, with attackers implementing the poisoning through ISP nodes, forcing users to access incorrect IP addresses. Examples of HTTP hijacking include users being forced to redirect to advertising or payment-inducing pages when accessing web pages on public Wi-Fi, or the presence of HTTP hijacking programs in routers that manipulate HTTP responses to insert advertisements. HTTPS websites are generally protected against HTTP hijacking, but the browsing experience on HTTP websites can be significantly impacted.
In FAQs, users often ask whether DNS poisoning and HTTP hijacking can occur simultaneously. The answer is yes. DNS pollution changes the IP address of the accessed website, while HTTP hijacking tampering with the HTTP content layer. The two can be combined, making the attack more effective. Some people have asked whether HTTPS can prevent DNS pollution. The answer is that HTTPS primarily protects content transmission and cannot directly prevent DNS pollution. However, combined with DNS over HTTPS or DNS over TLS, it can protect against both threats. To determine whether they are experiencing DNS pollution, ordinary users can use command-line tools such as nslookup or dig to query the domain name resolution IP address and compare it with the official IP address, or use a third-party DNS to test access. If a webpage is inaccessible or frequently redirects, be wary of DNS pollution. HTTP hijacking only affects HTTP websites, while the encrypted transmission of HTTPS websites is generally not tampered with unless there is a man-in-the-middle vulnerability. Enterprise protection measures include deploying an enterprise-level DNS security system, firewall policies, full-site HTTPS deployment, content security policies, internal network monitoring, and employee security education to improve overall protection capabilities.
In general, while DNS pollution and HTTP hijacking both disrupt user access, there are significant differences in the attack level, manifestation, scope of impact, and protection methods. DNS pollution attacks the domain name resolution portal, tampering with user access addresses. This has a wide impact but is difficult to detect. HTTP hijacking attacks HTTP content, tampering with user access content. This is highly visible but primarily affects HTTP traffic. Understanding the principles and differences between these two attacks can help users and enterprises choose effective protection strategies to ensure network access security and stability.
