Stub resolver hijacking is item 7 on the FIRST DNS Abuse Matrix. It refers to the modification of an operating system’s stub resolver, its host file, or its settings. Practically every communication on a computer network begins with a Domain Name System (DNS) query. As such, attacks on DNS have an enormous effect on any network connection. One hidden attack on operating systems is stub resolver hijacking, where a compromise operating system has its sub-resolver replaced or its settings changed to compromise DNS resolution.
What is Stub Resolver Hijacking?
A DNS stub resolver is an essential component of a computer or mobile operating system. It serves as an intermediary between applications, such as web browsers, and the recursive DNS resolver provided by the network. The DNS stub resolver performs the following process to find an answer to a query:
- Receives a DNS query from applications running on the computer.
- Checks the host file, normally /etc/hosts (Linux or MacOS) or C:\Windows\System32\drivers\etc\hosts (Windows) for an answer.
- Checks its local DNS cache for an answer.
- Forwards the query to the network-provided recursive server.
A DNS stub resolver hijack allows the attacker to perform various malicious activities, such as a DNS hijack, where legitimate domain requests are redirected to rogue servers, or a cache poisoning attack, which corrupts the DNS cache with false information. These attacks can lead to users being unknowingly directed to malicious websites, potentially resulting in data theft or other security breaches.
How does stub resolver hijacking happen?
Malware replaces the stub resolver.
Stub resolver hijacking often begins with malware infiltrating a device. The malware then replaces the stub resolver with a malicious version that intercepts DNS queries. This compromised resolver can then redirect users to fraudulent websites, steal sensitive information, or inject harmful code into legitimate websites.
Malware modifies the host’s file.
One common technique attackers use is modifying the host’s file on a device. The host file is a local file used to map domain names to IP addresses before DNS queries reach the resolvers. Malware can alter this file to include incorrect domain-to-IP mappings, effectively redirecting traffic from legitimate sites to malicious ones. This manipulation results in users unknowingly visiting fraudulent websites, which can lead to credential theft, phishing attacks, or the compromise of personal data.
Malware changes settings for upstream recursive servers.
Another method involves malware altering the settings that tell the stub resolver which upstream recursive servers to use. By changing DNS settings, attackers can reroute traffic through their malicious servers, gaining control over users’ online activities. This manipulation enables them to perform phishing attacks, data interception, and other malicious activities.
Examples of stub resolver hijacking.
DNSChanger malware is a notorious example of stub resolver hijacking. It infected millions of computers worldwide by altering recursive DNS settings, redirecting users to fraudulent websites filled with ads and malware. This attack highlighted the potential havoc that stub resolver hijacking can cause on a global scale.
ZeuS Trojan: Renowned for its proficiency in stealing banking credentials. It is not only focused on financial gain but also manipulates DNS settings to intercept sensitive information from unsuspecting users. By rerouting traffic, it can capture login details and other personal data, posing a significant threat to individual users and organizations.
Android Switcher: Malware targeting Android devices, modifying DNS settings to redirect traffic to phishing websites cleverly disguised as legitimate portals. By doing so, it tricked users into inputting sensitive information, such as login credentials and personal details, which could then be exploited by cybercriminals for various malicious purposes.
GhostDNS: A sophisticated type of malware that modifies the `/etc/hosts` file entries to misdirect users to malicious websites. By tampering with this file, GhostDNS can bypass DNS settings and direct users to phishing sites or pages filled with malicious content. This strategic manipulation allows attackers to capture sensitive information, such as login credentials and personal data, directly from the users themselves, posing significant privacy and security risks.
How stub resolver hijacking impacts your businesses.
Since DNS is a critical infrastructure component of an enterprise network, stub resolver hijacking impacts the business in a myriad of ways, depending on what the attacker does with their newfound access and ability to intercept network traffic.
DNS Compromise and Cache Poisoning.
For businesses, stub resolver hijacking is a serious security threat that compromises the integrity of the Domain Name System (DNS), potentially leading to cache poisoning. In this scenario, malicious actors can inject false information into the DNS cache, which allows them to redirect unsuspecting users to fraudulent websites designed to steal sensitive data, intercept login credentials, or distribute additional malware. This manipulation can have devastating effects, as users are often unaware they are being redirected to malicious sites. Such incidents not only damage a business’s reputation by associating it with security breaches but also jeopardize customer trust and loyalty.
Data breaches.
Stub resolver hijacking poses a significant threat to cybersecurity by redirecting users to malicious phishing sites specifically crafted to harvest sensitive information such as login credentials, personal identification data, and financial details. This tactic can lead to data breaches that have severe consequences for businesses, potentially exposing confidential data, trade secrets, and extensive customer records.
Regulatory fines and lawsuits.
The ramifications of a stub resolver hijack that compromises Personally Identifiable Information (PII) or regulated data often include substantial financial losses, damage to reputation, and legal repercussions, including potential lawsuits and penalties. To mitigate these risks, organizations must implement robust security measures and educate their employees on recognizing and preventing phishing attempts.
Preventing Stub Resolver Hijacking
Malware Protection.
Prevention begins with robust malware protection. Employing up-to-date antivirus software and regular system scans can detect and neutralize malicious code attempting to compromise the stub resolver. Furthermore, organizations must have policies in place to ensure that employees use trusted software sources and do not download or install unauthorized programs.
Implementing DNSSEC.
DNS Security Extensions (DNSSEC) is a protocol used to protect against DNS-related attacks, such as cache poisoning and stub resolver hijacking. It enhances the security of the Domain Name System by digitally signing DNS records with cryptographic keys. By doing so, DNSSEC ensures that responses from authoritative nameservers are authentic and have not been tampered with during transmission. This added layer of verification helps maintain the integrity of internet communications by preventing attackers from redirecting users to malicious sites.
Learn how to implement DNSSEC on Vercara’s UltraDNS.
Secure the host file.
To prevent unauthorized modifications that could lead to stub resolver hijacking, it is crucial to make the host file read-only. On a Windows system, you can do this by navigating to the host file location at `C:\Windows\System32\drivers\etc\hosts`. Right-click on the file, select ‘Properties,’ and under the ‘Attributes’ section, check the ‘Read-only’ box. For Linux or macOS systems, open a terminal and use the command `sudo chmod 444 /etc/hosts`. This will restrict write access, making it harder for malicious software to alter the file. These steps help ensure the host file remains secure, reducing the risk of stub resolver hijacking. Additionally, the host file can be monitored for changes with endpoint protection or file integrity solutions.
Use a protective DNS service.
Implementing a protective DNS service adds an extra layer of security to your network infrastructure. These services utilize real-time threat intelligence to monitor and block access to malicious domains, reducing the risk of phishing attacks and malware infections. By preventing DNS-based attacks, such as DNS spoofing and cache poisoning, these services enhance the overall security posture of organizations, ensuring that users can safely navigate the internet and access trusted resources without compromising sensitive data.
Use canary FQDNs to verify proper DNS resolution.
Canary Fully Qualified Domain Names (FQDNs) can act as early warning systems for potential security threats. By diligently monitoring DNS resolution accuracy, businesses can quickly identify any discrepancies that may be indicative of stub resolver hijacking. This process involves setting up specific FQDNs that, when resolved incorrectly, signal a potential compromise or interception of DNS queries. Implementing such a system enables organizations to proactively address and mitigate security vulnerabilities before they escalate into significant issues.
Security awareness training.
Given that many stub resolver hijacking attempts rely on social engineering tactics such as phishing emails, educating employees on how to identify and avoid these threats is critical. Organizations should conduct regular security awareness training sessions to keep staff up to date on the latest attack techniques and best practices for staying safe online.
The changes brought by DNSChanger.
The DNSChanger malware had a profound impact on businesses worldwide, disrupting daily operations and leading to significant financial losses. Many organizations found themselves grappling with network unavailability, as infected systems made it difficult for employees to access essential online resources. This loss of productivity, coupled with the cost of implementing emergency IT solutions, placed a strain on affected companies. Furthermore, businesses experienced a surge in security-related expenses as they invested in advanced cybersecurity infrastructure and incident recovery programs to prevent recurring threats.
Stub resolver hijacking poses a significant threat to businesses and individuals who still must keep operating even though the Internet has become more hostile over time. Understanding stub resolver hijacking, its potential impact, and effective prevention strategies are crucial for operating safely online.
How Vercara can help.
Vercara’s UltraDDR is a top-tier protective DNS service, implemented as a filtering DNS recursive server, designed to prevent attacks on endpoints. By combining recursive and private DNS resolver technologies, UltraDDR actively blocks harmful queries and tracks adversary infrastructure. It includes robust security measures to ensure its servers remain uncompromised. Additionally, the UltraDDR endpoint client removes the reliance on network-provided recursive servers, such as those found in coffee shops or hotels, which can be compromised.
Vercara’s UltraDNS is an authoritative DNS platform meticulously designed to prevent DNS server compromises and other malicious attacks. It offers robust security features and reliable performance, ensuring that your domain name system is always protected and operates efficiently. It supports an easy implementation of DNSSEC, which mitigates the risks associated with stub resolver hijacking.
For those seeking further information and resources, consider exploring our advanced security solutions and engaging with our team of cybersecurity professionals to fortify your defenses against stub resolver hijacking and other emerging threats.
