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Ghost DNS Record

Threat NG Staff

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a DNS entry that continues to exist and resolve, even though the resource it points to (such as a website or server) is no longer active, available, or under the control of its original owner.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:

  1. 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.

  2. 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    • The DNS record remains in the DNS zone file, even though the resource it points to is no longer valid or accessible.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.

  3. Attacker Identification:

    • A malicious actor discovers this ghost DNS record and realizes the potential for exploitation.

  4. 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.

  5. 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.

  6. 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  • Regular DNS audits and prompt cleanup of unused or outdated records are crucial for preventing such attacks.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's robust capabilities offer a comprehensive solution for identifying and mitigating vulnerabilities that could lead to subdomain takeovers, including those arising from "Ghost DNS records." It leverages its investigation modules and continuous monitoring to provide proactive protection.

Key ThreatNG Components in Subdomain Takeover Prevention:

  • Domain Intelligence:

    • DNS Intelligence: Scans DNS records, identifying "ghost" entries pointing to inactive or non-existent resources.

    • Subdomain Intelligence: Discovers and assesses all subdomains, highlighting inactive or misconfigured ones.

    • Certificate Intelligence: Monitors SSL certificates for expiration or mismatches, which could indicate an unclaimed or vulnerable subdomain susceptible to takeover.

  • Cloud and SaaS Exposure:

    • Sanctioned/Unsanctioned Cloud Services: Discovers cloud resources, pinpointing decommissioned services with lingering DNS records.

    • Cloud Service Impersonations: This feature detects potential attempts by attackers to impersonate the organization's cloud services, a possible precursor to a subdomain takeover.

  • Archived Web Pages:

    • Subdomains and Directories: Analyzes archived web pages to identify defunct subdomains or services that might have lingering, "ghost" DNS records.

ThreatNG's Workflow to Counteract Ghost DNS Records and Subdomain Takeovers:

  1. Discovery: ThreatNG's Domain Intelligence module employs DNS Intelligence to scan and analyze the organization's DNS records actively.

  2. Identification: It identifies DNS entries that point to resources no longer active or controlled by the organization, flagging them as potential "ghost" records.

  3. Assessment: ThreatNG assesses the Subdomain Takeover Susceptibility of these identified "ghost" records, considering factors like CNAME configurations, resource availability, and external threat intelligence.

  4. Alerting and Reporting: Security teams receive immediate alerts and detailed reports about the discovered ghost DNS records and their associated risks.

  5. Remediation: ThreatNG provides actionable recommendations for remediation, such as removing the ghost record, reconfiguring the subdomain, or taking ownership of the unclaimed resource.

Integration with Complementary Solutions:

ThreatNG further strengthens its defense against subdomain takeovers by integrating with other security tools:

  • Vulnerability Scanners: Correlates findings with DNS data to identify subdomains with exploitable weaknesses.

  • Web Application Firewalls (WAFs): Can be configured to block traffic to or from suspicious subdomains identified by ThreatNG.

  • Security Information and Event Management (SIEM) Systems: Feeds subdomain takeover alerts into SIEMs for centralized monitoring and incident response.

ThreatNG's combination of proactive discovery, continuous monitoring, and actionable intelligence enables organizations to effectively combat the threat of subdomain takeovers arising from ghost DNS records.