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Stale DNS Entry

Threat NG Staff

A stale DNS entry, much like a dangling or orphaned DNS record, is a DNS configuration that points to a resource (such as a website or server) that is no longer active, available, or under the control of its original owner. This often happens when services are decommissioned, migrated to new platforms, or domains expire without proper DNS record management.

How it can lead to a Subdomain Takeover:

  1. Resource Decommissioning or Expiration: A company might shut down a service, migrate it to a new provider, or let a domain name expire.

  2. Stale DNS Record Persists: The DNS records associated with the decommissioned or expired resource are not updated or removed, leaving them "stale" and pointing to a non-existent or unclaimed resource.

  3. Attacker Identification: A malicious actor discovers the stale DNS record and recognizes the opportunity to exploit it.

  4. Resource Recreation: The attacker creates a new resource (e.g., a website server) on the same platform or configuration as the original, now-defunct resource.

  5. Subdomain Takeover: Because the stale DNS record still points to the original resource's location, it inadvertently directs traffic to the attacker's newly created resource.

  6. Malicious Activity: The attacker now has control over the subdomain and can use it for various malicious purposes, including:

    • Phishing: Creating a fake login page to steal user credentials

    • Malware Distribution: Hosting malware or malicious scripts

    • Traffic Redirection: Redirecting users to malicious websites

    • Brand Damage: Tarnishing the reputation of the original domain owner

Key Points to Remember:

  • Stale DNS entries are a severe security risk that can enable subdomain takeovers.

  • Regular DNS audits and prompt cleanup of unused or outdated records are essential for preventing such attacks.

  • CNAME records are particularly vulnerable to subdomain takeovers as they directly point to another domain or hostname.

  • Subdomain takeovers can have significant consequences, including data breaches, financial loss, and damage to brand reputation.

How ThreatNG Helps Mitigate Subdomain Takeover Risks:

ThreatNG's robust capabilities offer a comprehensive approach to identifying and mitigating subdomain takeover vulnerabilities, leveraging its investigation modules and continuous monitoring.

Key ThreatNG Components in Subdomain Takeover Prevention:

  • Domain Intelligence:

    • DNS Intelligence: Continuously scans DNS records, identifying stale or misconfigured entries (e.g., CNAMEs pointing to non-existent services) that are prime targets for takeovers.

    • Subdomain Intelligence: Discovers all subdomains, active and inactive, assessing their configurations and potential vulnerabilities.

    • Certificate Intelligence Monitors SSL certificates for expirations or mismatches, which can allow attackers to take over subdomains.

  • Cloud and SaaS Exposure:

    • Sanctioned/Unsanctioned Cloud Services: Identifies cloud services used by the organization, highlighting shadow IT that may have misconfigured DNS entries.

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

  • Sensitive Code Exposure:

    • Exposed Public Code Repositories: Scans public code repositories for leaked credentials or configuration files that could provide access to DNS management systems.

  • Archived Web Pages:

    • Subdomains, Directories, Usernames: This capability analyzes archived web pages to identify defunct subdomains or services with lingering DNS entries.

  • Dark Web Presence:

    • Organizational Mentions: Monitors dark web forums for discussions about potential subdomain takeovers targeting the organization.

    • Compromised Credentials: Identifies leaked credentials that could be used to gain unauthorized access to DNS management.

How ThreatNG Works with Complementary Solutions:

ThreatNG integrates with other security tools to enhance subdomain takeover prevention:

  • Vulnerability Scanners: Correlates findings from vulnerability scans with DNS information to identify subdomains with exploitable weaknesses.

  • Web Application Firewalls (WAFs): Configures WAF rules to block traffic to or from potentially compromised subdomains.

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

Examples:

  1. Stale CNAME Record: ThreatNG's DNS Intelligence module flags a CNAME record pointing to a decommissioned marketing platform. This is assessed as a high Subdomain Takeover Susceptibility, prompting immediate remediation.

  2. Exposed Cloud Bucket: The Cloud and SaaS Exposure module discovers an open AWS S3 bucket containing configuration files with DNS API keys. ThreatNG alerts the team to this critical risk, preventing potential unauthorized DNS changes.

  3. Leaked Credentials on Dark Web: The Dark Web Presence module detects discussions about leaked credentials of an employee with DNS management access. The security team is alerted, and the credentials are promptly reset.

ThreatNG's combination of continuous monitoring, profound asset discovery, and intelligence analysis allows it to proactively identify and mitigate subdomain takeover risks, safeguarding organizations from this critical attack vector.