DNS Cache Poisoning
DNS cache poisoning is a cyberattack where an attacker injects fraudulent DNS data into a DNS resolver's cache. This causes the name server to return an incorrect IP address for a legitimate domain, redirecting users to a malicious website without their knowledge. It is also known as DNS spoofing.
How DNS Cache Poisoning Works
The Domain Name System (DNS) acts as the Internet's phonebook, translating human-readable domain names (like example.com) into numerical IP addresses. To speed up this process, DNS resolvers store information from previous queries in a temporary local storage called a cache.
In a DNS cache poisoning attack, the attacker exploits vulnerabilities in the DNS protocol to insert a forged IP address into the cache. When a user tries to access a legitimate website, their request goes to the poisoned DNS resolver, which then provides the fake IP address from its cache. The user's browser is then sent to the attacker's fraudulent website, which often looks identical to the real one.
Attackers can use several methods to achieve this:
Direct Server Hijacking: An attacker directly compromises a DNS server to modify its records and reroute traffic to a malicious IP address.
Man-in-the-Middle (MITM) Attacks: The attacker positions themselves between a user and a DNS server and intercepts the DNS query. They then send a forged DNS response to the user's device before the legitimate server can reply.
Exploiting Protocol Weaknesses: The DNS protocol primarily uses the User Datagram Protocol (UDP), which does not have built-in authentication. Attackers exploit this by guessing the correct transaction ID and source port of a DNS query and flooding the DNS resolver with a forged response before the legitimate one arrives.
Consequences of a DNS Cache Poisoning Attack
The consequences of a successful DNS cache poisoning attack can be severe for both users and organizations.
Phishing and Data Theft: Attackers redirect users to fake websites to trick them into entering sensitive information, such as login credentials, credit card numbers, and other personal data, which the attacker can then steal or sell.
Malware Distribution: The fake website can be used to deliver malware or spyware to a user's device, either through a malicious download link or a drive-by download.
Reputation Damage: For businesses, a successful DNS cache poisoning attack can lead to financial losses, data manipulation, and a loss of customer trust and image.
Prevention
DNSSEC: The Domain Name System Security Extensions (DNSSEC) protocol adds a layer of security to DNS by cryptographically signing DNS data. This allows a DNS resolver to verify that a response is from an authoritative source and has not been tampered with.
Regular Updates: Regularly updating and patching DNS software helps to fix known vulnerabilities that attackers can exploit.
End-to-End Encryption: Using services that encrypt DNS traffic, such as DNS over HTTPS (DoH), can help prevent attackers from intercepting and altering DNS queries.
Randomization: Modern DNS resolvers use randomization to make it more difficult for attackers to guess the correct transaction ID and source port of a DNS query.
ThreatNG helps with DNS cache poisoning by identifying and assessing external vulnerabilities in an organization's DNS infrastructure before attackers can exploit them. It works from an outside-in perspective, mapping out the domains and subdomains that are reliant on DNS to reveal potential weaknesses.
External Discovery and Assessment
ThreatNG's External Discovery can find an organization's DNS infrastructure without authentication, allowing it to map out its online presence. The External Assessment capabilities can then assess the security posture of this infrastructure and identify potential misconfigurations or vulnerabilities that could be exploited in a DNS cache poisoning attack.
Cyber Risk Exposure: This score considers parameters that ThreatNG's Domain Intelligence module covers, including certificates and subdomain headers, to determine the overall cyber risk. An insecure DNS server with exposed sensitive ports would increase this score.
Subdomain Takeover Susceptibility: ThreatNG directly analyzes risks related to DNS configuration by performing a comprehensive analysis of subdomains, DNS records, and other relevant factors to identify vulnerabilities or misconfigurations that could lead to a subdomain takeover. This is crucial as a subdomain takeover often relies on manipulating DNS records.
For example, ThreatNG could assess an organization's domain and find that a DNS server is not configured to restrict zone transfers. This vulnerability could allow an attacker to obtain a copy of the DNS zone file and map out the network for a DNS spoofing attack.
Investigation Modules
ThreatNG's Investigation Modules provide detailed analysis that is critical for investigating DNS cache poisoning threats.
Domain Intelligence: This module provides a comprehensive view of an organization's domain-related assets. Its DNS Intelligence feature specifically analyzes DNS records for errors, inconsistencies, or potentially malicious configurations. For example, ThreatNG can identify if a domain's DNS records have been recently and unexpectedly modified, which could indicate a DNS spoofing attempt.
Certificate Intelligence: This module analyzes TLS certificates associated with domains and subdomains. This is important for DNS spoofing, as the attacker's fake website may not have a valid certificate, which is a key indicator that a user has been redirected to a malicious site.
Intelligence Repositories
ThreatNG's continuously updated Intelligence Repositories (DarCache) provide crucial context for DNS cache poisoning investigations.
Vulnerabilities (DarCache Vulnerability): This repository helps prioritize risks by providing a holistic view of external vulnerabilities. By using data from NVD, EPSS, and KEV, ThreatNG can identify vulnerabilities in DNS server software that could be exploited to launch a DNS cache poisoning attack.
Compromised Credentials (DarCache Rupture): This repository tracks compromised credentials on the dark web. An attacker who obtains legitimate credentials from the dark web could potentially use them to gain access to a DNS server to modify records and initiate a DNS cache poisoning attack.
Dark Web (DarCache Dark Web): This repository tracks mentions of an organization on the dark web, which can be an early indicator of a planned phishing or impersonation campaign that may use a compromised DNS server.
Reporting and Continuous Monitoring
ThreatNG provides various reports, including Prioritized (High, Medium, Low, and Informational) and Security Ratings (A through F), which can detail the findings of its DNS security tests. The reports include risk levels, reasoning, and recommendations to help security teams prioritize their efforts. ThreatNG's Continuous Monitoring capability constantly monitors the external attack surface for changes in DNS records, new subdomains, and other DNS-related activities that could indicate potential security risks or a DNS cache poisoning attempt. This allows organizations to respond proactively.
Complementary Solutions
ThreatNG's capabilities can be used with complementary security solutions to enhance an organization's defense against DNS cache poisoning.
DNS Protection Services: ThreatNG can identify misconfigured DNS servers or vulnerable DNS records. This information can be used by a DNS protection service to block users from accessing fraudulent sites that are the result of DNS cache poisoning.
Security Information and Event Management (SIEM) Systems: ThreatNG's continuous monitoring and reporting capabilities can feed alerts and intelligence directly into a SIEM system. For example, suppose ThreatNG detects an unauthorized change to a critical DNS record or a suspicious domain permutation. In that case, it can alert the SIEM, which can then correlate this information with internal logs to provide a more holistic view of the potential threat.
