Ghost DNS Record
A "Ghost DNS record" is essentially the same as a "dangling," "stale," or "zombie" DNS record. It refers to a DNS entry that continues to exist and resolve, even though the resource it points to (such as a website or server) is no longer active, available, or under the control of its original owner.
How it Can Lead to a Subdomain Takeover:
The process by which a ghost DNS record can result in a subdomain takeover is as follows:
Resource Decommissioning or Expiration:
A company might shut down a service, migrate it to a new platform, or let a domain name expire.
Sometimes, DNS records may be inadvertently left behind during infrastructure changes or migrations.
Ghost DNS Record Persists:
The DNS record remains in the DNS zone file, even though the resource it points to is no longer valid or accessible.
This can happen due to oversight, lack of proper DNS management, or issues with DNS propagation.
Attacker Identification:
A malicious actor discovers this ghost DNS record and realizes the potential for exploitation.
Resource Recreation:
The attacker creates a new resource (e.g., a website, server) on the same platform or with a similar configuration as the original resource that the ghost DNS record points to.
Subdomain Takeover:
Since the ghost DNS record is still active and resolving, it inadvertently directs traffic to the attacker's newly created resource.
Users attempting to access the original, now-defunct resource will be unknowingly redirected to the attacker's controlled environment.
Malicious Activity:
The attacker has now effectively taken control of the subdomain and can use it for various malicious purposes, such as:
Phishing: Creating fake login pages to steal user credentials
Malware Distribution: Hosting malware or malicious scripts
Traffic Redirection: Redirecting users to other malicious websites
Brand Damage: Tarnishing the reputation of the original domain owner by associating it with malicious activity
Key Takeaways
Ghost DNS records are a serious security risk that can facilitate subdomain takeovers.
Regular DNS audits and prompt cleanup of unused or outdated records are crucial for preventing such attacks.
CNAME records are particularly vulnerable to subdomain takeovers, as they directly point to other domains or hostnames.
Organizations must prioritize proper DNS hygiene to avoid the potential consequences of subdomain takeovers, which can result in data breaches, financial loss, and damage to brand reputation.
Remember, the term "ghost" emphasizes the lingering presence of the DNS record even though the associated resource is no longer there, creating an exploitable vulnerability for attackers.
ThreatNG is exceptionally well-suited to detect and address "Ghost DNS Records" because it focuses on external, unauthenticated discovery and its granular DNS intelligence. By their very nature, these records are often "forgotten or abandoned" and thus invisible to internal systems, making ThreatNG's outside-in perspective crucial.
ThreatNG performs purely external, unauthenticated discovery without needing connectors. This is paramount for uncovering "ghost DNS records," which exist publicly but are often no longer tracked internally.
Example: ThreatNG can systematically map all DNS records associated with an organization's domains and subdomains, including those pointing to decommissioned services or third-party providers that have since been abandoned. This uncovers the "ghosts" that are still publicly visible.
ThreatNG's external assessment capabilities directly identify risks associated with ghost DNS records:
Subdomain Takeover Susceptibility: ThreatNG directly evaluates a website's subdomain takeover susceptibility using external attack surface and digital risk intelligence that incorporates Domain Intelligence. This intelligence includes comprehensively analyzing the website's subdomains, DNS records, and SSL certificate statuses.
Example: ThreatNG can flag a CNAME record that points to an abandoned external service (e.g., an old cloud platform or a defunct PaaS provider). This identifies a prime "ghost DNS record" vulnerability where an attacker could claim the external service and effectively take over the subdomain, using it for phishing or brand impersonation, even if the organization believes the asset is decommissioned.
Cyber Risk Exposure: This score considers parameters our Domain Intelligence module covers, including certificates, subdomain headers, vulnerabilities, and sensitive ports.
Example: If a ghost A record points to an old, unpatched IP address that is still public, ThreatNG can factor this into the Cyber Risk Exposure score by identifying known vulnerabilities associated with services running on that IP, indicating a forgotten attack surface.
3. Reporting:
ThreatNG provides various reports that are crucial for highlighting and addressing ghost DNS records:
Prioritized Report: Can highlight subdomains vulnerable to takeover due to ghost DNS records as high-priority risks, demanding immediate attention.
Inventory Report: Can list all discovered external assets, including subdomains and their associated DNS records, allowing an organization to audit and clean up "ghosts" that are still public.
Security Ratings Report: Can reflect the impact of exposed ghost DNS records on an organization's overall external security posture, particularly its Subdomain Takeover Susceptibility and Cyber Risk Exposure scores.
ThreatNG offers continuous monitoring of all organizations' external attack surfaces, digital risks, and security ratings. This is vital for detecting new or emerging ghost DNS records and confirming the remediation of old ones.
Example: ThreatNG can continuously scan for changes in DNS records. Suppose a new CNAME pointing to an abandoned external service appears (perhaps due to a misconfiguration during a migration). In that case, ThreatNG can alert the security team immediately, preventing a subdomain takeover before it occurs. After a remediation attempt, it can also verify that a ghost record has been removed.
ThreatNG's investigation modules provide granular detail for deeply analyzing ghost DNS records:
Domain Intelligence: This module is central to uncovering ghost DNS records.
DNS Intelligence (Domain Record Analysis): Provides "IP Identification, Vendors and Technology Identification". It can map all DNS records, including A, CNAME, MX, TXT, etc., to identify outdated or unintended entries.
Example: An analyst can use Domain Record Analysis to identify a CNAME record for
old-blog.yourcompany.compointing to a discontinued blogging platform, revealing it as a "ghost" takeover target.
Subdomain Intelligence (Subdomain Takeover Susceptibility): Directly assesses if subdomains are vulnerable due to misconfigured DNS records or abandoned external services.
Example: ThreatNG's Subdomain Intelligence can provide detailed information on why
dev.yourcompany.comis vulnerable to takeover, specifically pointing to an outdated CNAME record.
IP Intelligence: Provides information about IPs, shared IPs, ASNs, and country locations.
Example: If a ghost A record points to an IP that the organization no longer controls, IP Intelligence can identify the current owner of that IP, helping determine the risk.
6. Intelligence Repositories (DarCache):
ThreatNG's DarCache repositories provide context and threat intelligence relevant to the risks posed by ghost DNS records:
DarCache Vulnerability (NVD, EPSS, KEV, PoC Exploits): Provides a holistic and proactive approach to managing external risks and vulnerabilities.
Example: If a ghost DNS record points to a server running an application with a known, actively exploited vulnerability (KEV), DarCache Vulnerability can highlight this, providing immediate context on the severity of the "ghost."
DarCache Dark Web: Monitors for mentions of the organization.
Example: While not directly finding ghost records, this could detect discussions on the dark web about how to exploit a known subdomain takeover vulnerability, giving context to the threat posed by lingering DNS entries.
Complementary Solutions:
ThreatNG's external insights create powerful synergies with other security solutions to combat ghost DNS records:
Domain Name Registrars/DNS Management Tools: ThreatNG's discovery of ghost DNS records (e.g., outdated CNAMEs or A records pointing to forgotten infrastructure) can inform an organization's DNS management team or registrar. This allows for precise cleanup and removal of the "ghosts" within their authoritative DNS.
Cloud Security Posture Management (CSPM) Tools: ThreatNG's identification of subdomains vulnerable to takeover because they point to abandoned cloud resources can be cross-referenced with CSPM tools. While CSPM focuses on actively managed cloud environments, ThreatNG identifies the legacy pointers that could be exploited. This helps ensure that even remnants of cloud infrastructure are properly secured or decommissioned.
Security Orchestration, Automation, and Response (SOAR) Platforms: ThreatNG's real-time alerts on newly detected subdomain takeover vulnerabilities caused by ghost DNS records can trigger automated playbooks in a SOAR platform. This could involve automatically opening a ticket for the security operations center (SOC) or IT team, initiating a follow-up internal validation, or even generating an automatic request to remove the problematic DNS record.
Brand Protection Platforms: ThreatNG's ability to detect potential subdomain takeovers due to ghost DNS records provides a critical early warning for brand protection platforms. These platforms can then initiate rapid takedown processes if a legitimate subdomain is compromised and used for phishing or brand impersonation, minimizing damage. Actionable intelligence enables organizations to effectively combat the threat of subdomain takeovers arising from ghost DNS records.
