What is DNS hijacking, and what are its risks?

　　DNS is the system that translates domain names into IP addresses. When you enter a web address, DNS tells you which server to connect to. DNS hijacking occurs when someone tampers with this "translation chain," redirecting a domain name—which should point to the legitimate server—to an address specified by the attacker.

　　Attackers primarily use three methods to tamper with resolution records: hijacking local devices (modifying your computer's hosts file or DNS settings), hijacking routers (altering your home router's DNS configuration, thereby affecting all connected devices), and attacking DNS servers (including DNS cache poisoning, compromising authoritative DNS servers, and man-in-the-middle attacks).

　　Having covered the methods, this article focuses on the risks—specifically, the consequences of DNS hijacking and why it is far more serious than many people realize.

　　Risk 1: Theft of account credentials—the most immediate loss.

　　A classic scenario for DNS hijacking is phishing.

　　Attackers redirect the domain names of banking websites, e-commerce platforms, or email login pages to a meticulously crafted fake site. This counterfeit site looks identical to the real one—the logo, layout, input fields, and even the SSL certificate appear flawless.

　　When you enter your username and password and click "Log In," the page might even redirect you back to the genuine site, leading you to believe it was merely a momentary network glitch. However, your credentials have already been captured by the attacker's server.

　　The severity of this risk depends on the type of website hijacked:

　　Banking and payment platforms—Direct financial loss. Once attackers obtain your online banking credentials, they can transfer funds, make purchases, or apply for loans.

　　Email services—Email accounts often serve as the gateway for password recovery across many other services. If an email account is compromised, attackers can use it to reset passwords for your other accounts, triggering a chain reaction.

　　Corporate and internal systems—If the domain used for employee logins is hijacked, attackers can steal employee credentials and subsequently gain access to the corporate internal network.Social media and e-commerce accounts—once compromised, they can be used to scam your contacts or make unauthorized charges using your linked payment methods.

　　Risk 2: Traffic hijacked to malicious servers; website fully compromised

　　Traffic redirection is a threat even more insidious than phishing.

　　Instead of forging a login page, attackers redirect your domain's resolution to a malicious server. This server can:

　　Inject malicious code—when your website is opened, the page returned by the malicious server contains embedded cryptocurrency mining scripts, Trojan download links, or JavaScript designed to steal cookies. Users visiting your site end up infecting their own computers.

　　Tamper with website content—attackers can publish false information, scam advertisements, or even politically sensitive content on your site. For corporate websites, this directly damages brand reputation.

　　Intercept API communications—if the backend interfaces for your mini-program or app are redirected, attackers can perform a "man-in-the-middle" attack to intercept all API requests and responses, stealing user data, altering transaction amounts, or forging server commands.

　　Inject advertisements—this is a classic tactic of ISP-level DNS hijacking. When you visit a legitimate site, ads are forcibly injected at the top or bottom of the page—ads that have no connection to the site itself. Unsuspecting users may assume the site is displaying the ads, thereby damaging the site's brand image.

　　Risk 3: Corporate emails intercepted; trade secrets leaked

　　Corporate email systems typically use custom domains (e.g., name@company.com). If the domain's MX record is hijacked via DNS, attackers can:

　　Intercept all incoming and outgoing emails—attackers point the MX record to their own mail server, ensuring all emails destined for the company reach them first. Attackers can read the contents, forward them to the intended recipients (who remain completely unaware), or simply withhold them.

　　Forge sender identity—attackers can use the hijacked domain to impersonate company executives and send emails to finance staff, requesting fund transfers. This type of "Business Email Compromise" (BEC) causes billions of dollars in losses for businesses worldwide each year.

　　Theft of trade secrets—if ongoing M&A negotiations or product R&D discussions are conducted via email, all such information is exposed to the attacker.

　　Even more troublesome is that email hijacking can go undetected for weeks or even months. Since emails appear to be delivered normally, only the attacker knows that an extra "relay point" has been inserted into the process.

　　Risk 4: SSL certificate validation fails; HTTPS becomes ineffective

　　Many people assume that "a website is safe if it displays the HTTPS padlock icon." However, DNS hijacking can bypass this line of defense.

　　After redirecting the domain to their own server, attackers can obtain a free SSL certificate for that domain from Let’s Encrypt (since Let’s Encrypt verifies domain control rather than actual identity). Consequently, the browser address bar still displays HTTPS and the padlock icon, but the connection actually leads to the attacker.

　　Worse still, if attackers control DNS resolution, they can even apply for an EV (Extended Validation) certificate, which typically causes the browser address bar to display the company name. Seeing the company name (e.g., "XX Bank") alongside the padlock icon makes users even more convinced that the site is legitimate.

　　HTTPS protects the data transmission process but does not verify the authenticity of the server being connected to. DNS hijacking specifically targets the connection destination—the server itself. This is a common blind spot in understanding.

　　Risk 5: SEO rankings plummet; organic traffic drops to zero

　　This risk is particularly devastating for corporate websites, yet many fail to realize it.

　　Search engine crawlers also rely on DNS resolution to crawl web pages. If your domain is hijacked via DNS, the content crawled by search engines may actually be hosted on the attacker's server—such as spam pages, gambling sites, or simply 404 error pages.

　　Search engines may conclude that your website suffers from "declining content quality" or "security issues," leading them to lower your ranking or even remove your site from search results entirely. By the time you notice, organic traffic will have plummeted, and recovering your rankings will take a long time.

　　There is also a more insidious scenario: attackers redirect your domain to a "mirror site." This mirror site copies all your content but injects a multitude of black-hat SEO links. Search engines may struggle to distinguish the "authentic" site from the copy, potentially causing your original content to be flagged as "plagiarism."

　　Risk 6: A Launchpad for DDoS Attacks

　　DNS hijacking isn't just about being a passive victim; it can also turn your server into a tool for attacking others.

　　If attackers control your DNS resolution, they can point your domain toward a victim's server. When large numbers of users visit your domain, the traffic actually hits the victim's server—effectively turning your users into unwitting accomplices in a DDoS attack, while the victim remains completely unaware of the attack's true source.

　　In another scenario, attackers hijack your DNS to redirect your domain to a malware distribution server. Users visiting your domain end up downloading malware, and your domain gets flagged as "malicious" on security vendors' blacklists. Getting removed from these blacklists can take weeks or even months.

　　Risk 7: Brand Reputation Damage and Loss of User Trust

　　This is the ultimate consequence of all these technical risks.

　　When users visit your site, they might encounter tampered pages, injected advertisements, or browser warnings stating that the site is unsafe. They won't investigate to see if DNS hijacking is the cause; they will simply remember that "there is something wrong with this site."

　　For e-commerce platforms, users become afraid to place orders; for financial institutions, they hesitate to log in; for corporate websites, clients begin to question the company's professionalism. Once trust collapses, the cost of rebuilding it far exceeds the cost of technical repairs.

　　Who Is Most Likely to Be Targeted?

　　DNS hijacking is not a random attack; attackers usually select their targets deliberately:

　　Financial institutions and payment platforms—these offer the highest potential for direct financial gain. E-commerce platforms—Users have linked payment methods, making the accounts valuable.

　　Corporate email systems—Gateways to trade secrets and Business Email Compromise (BEC) fraud.

　　Government and educational websites—High traffic volume; hijacking them has a widespread impact.

　　High-traffic websites—Hijacking allows for the injection of ads or cryptomining scripts, enabling quick monetization.

　　Small and medium-sized websites using cheap or free DNS services—Weak security defenses, making them easy targets.

　　How can you tell if you have been hijacked? Here are a few simple self-check methods:

　　Compare DNS resolution results across different networks. Access the same website using your mobile 4G connection and your home Wi-Fi; if the results differ (one normal, one abnormal), you may have been hijacked.

　　Check the hosts file. Open `C:\Windows\System32\drivers\etc\hosts` (Windows) or `/etc/hosts` (macOS/Linux) and look for any unfamiliar domain mapping records.

　　Check router DNS settings. Log in to the router's admin interface and view the DNS addresses in the WAN and DHCP settings. If they are not addresses you recognize (such as 114.114.114.114 or 8.8.8.8), they may have been altered.

　　Verify using `dig` or `nslookup`. If the IP addresses returned by two different DNS servers do not match, it indicates that at least one of them has been compromised (poisoned).

　　Pay attention to SSL certificate warnings. When visiting sensitive websites, if your browser warns that the certificate is invalid or untrusted, you may have been redirected to a phishing site.

　　Monitor for abnormal website traffic. If organic search traffic suddenly plummets, or if users report that the site won't load or the page looks incorrect, you should investigate the DNS configuration.

　　Protection Strategies

　　The chain of harm caused by DNS hijacking begins with the tampering of the resolution process; therefore, protection measures should focus on this stage:

　　For general users: Enable encrypted DNS queries (DoH/DoT), change the router's default password, and periodically check the hosts file and DNS settings. For website operators: Enable DNSSEC (Domain Name System Security Extensions) to verify the authenticity of resolution results, use a reliable DNS provider, monitor for DNS hijacking or tampering, and enable two-factor authentication (2FA) for domain registrar accounts.

　　For enterprises: Deploy DNS security monitoring, train employees to recognize phishing attempts, and use dedicated domains and specialized DNS services for critical business systems.

　　In summary: The dangers of DNS hijacking go far beyond the simple inability to access a website. It can lead to compromised accounts, victimized users, exposed emails, and a ruined brand reputation. Yet, it all might stem from something as trivial as an unchanged default router password or a DNS record without DNSSEC enabled.