Hackable Subdomains
In cybersecurity, "hackable subdomains" refer to subdomains of a primary domain that are vulnerable to exploitation or unauthorized access by malicious actors. These vulnerabilities can stem from various misconfigurations, outdated software, or insecure practices, making the subdomain a potential entry point for attacks against an organization's entire digital presence.
Here's a detailed breakdown:
What are Subdomains? Subdomains are prefixes to a primary domain name (e.g., blog.example.com, shop.example.com, dev.example.com where example.com is the primary domain). Organizations use them to organize and manage different services, departments, or applications within their online infrastructure.
How Subdomains Become Hackable (Common Vulnerabilities):
Subdomain Takeovers: This is a particularly prevalent and dangerous type of hackable subdomain. It occurs when an attacker gains control of a subdomain because its DNS (Domain Name System) record points to a service or platform that is no longer in use or was never properly provisioned.
Dangling DNS Records: An organization might configure a DNS CNAME record for a subdomain to point to a third-party service (e.g., a cloud hosting provider, a content delivery network, a customer support platform). If the organization later deprovisions or cancels that third-party service but fails to remove the corresponding DNS entry, the subdomain effectively "dangles."
Attacker Exploitation: A malicious actor can then register an account on the same third-party service and claim the dangling subdomain. Once claimed, they can host their malicious content (e.g., phishing pages, malware, fake login forms) under the legitimate-looking subdomain. Users, seeing the trusted domain name, are more likely to fall for such attacks.
Misconfigurations:
Insecure Settings: Subdomains might be set up with default or insecure configurations, such as open ports, unnecessary services, or weak permissions, making them easier targets for attackers.
Open Directories: If a subdomain's web server is misconfigured to allow directory listing, attackers can browse and download sensitive files.
Outdated or Unpatched Software:
Subdomains often run their web applications (e.g., content management systems like WordPress, e-commerce platforms, custom applications), web servers (Apache, Nginx), or plugins. If these are not kept up-to-date with the latest security patches, they can contain known vulnerabilities that attackers can use.
Weak Authentication and Access Control:
Subdomains that lack strong authentication mechanisms (e.g., weak passwords, no multi-factor authentication) or have improperly configured access controls can allow unauthorized users to gain access to sensitive data or functionality.
Insecure Development Practices:
Web applications hosted on subdomains can contain security flaws introduced during development, such as:
SQL Injection: Allowing attackers to manipulate database queries.
Cross-Site Scripting (XSS): Enabling attackers to inject malicious scripts into web pages viewed by other users.
Input Validation Flaws: Insufficient checking of user input, leading to various vulnerabilities.
Third-Party Integrations:
Subdomains may integrate with third-party services or APIs. If these integrations are not appropriately secured (e.g., insecure data transmission, improper API key management), they can introduce security risks.
Why Hackable Subdomains are a Serious Concern:
Entry Point for Larger Attacks: A compromised subdomain can serve as a stepping stone for attackers to penetrate the organization's broader network, leading to ransomware infections, data breaches, or unauthorized access to sensitive internal systems.
Brand Reputation Damage: Attacks originating from a seemingly legitimate subdomain can severely damage an organization's reputation and customer trust.
Phishing and Malware Distribution: Attackers can host compelling phishing pages or distribute malware from a trusted subdomain, increasing their success rate.
Circumventing Security Measures: A compromised subdomain may bypass specific security measures designed for the main domain, as it's often considered part of the trusted infrastructure.
Prevention and Mitigation:
Organizations should implement a comprehensive cybersecurity strategy to address hackable subdomains, including:
Continuous Subdomain Enumeration and Monitoring: Regularly discover and inventory all active and inactive subdomains.
Vulnerability Scanning and Penetration Testing: Periodically assess subdomains for known vulnerabilities and misconfigurations.
Strict DNS Management: Carefully manage DNS records, promptly removing entries for deprovisioned services.
Secure Development Lifecycle: Incorporate security best practices into the development of all web applications hosted on subdomains.
Regular Software Updates: Keep all software, plugins, and systems running on subdomains up to date and patched.
Robust Authentication and Access Control: Implement strong authentication methods and enforce the principle of least privilege.
External Attack Surface Management (EASM) solutions: Use tools that provide comprehensive visibility into an organization's digital footprint to identify and mitigate risks associated with subdomains.
ThreatNG offers a comprehensive solution for addressing hackable subdomains through its various capabilities, ensuring a proactive and in-depth approach to external cybersecurity.
External Discovery: ThreatNG excels in purely external, unauthenticated discovery, meaning it can identify subdomains and their associated vulnerabilities from an attacker's perspective without needing any internal connectors. This enables organizations to view their attack surface from the perspective of a malicious actor, uncovering potential entry points that might otherwise be overlooked.
External Assessment: ThreatNG provides detailed assessments that directly address the various ways subdomains can become hackable:
Subdomain Takeover Susceptibility: ThreatNG directly evaluates a website's susceptibility to subdomain takeover. It uses external attack surface and digital risk intelligence, incorporating Domain Intelligence, which includes a comprehensive analysis of the website's subdomains, DNS records, and SSL certificate statuses. This helps identify dangling DNS records that could lead to subdomain takeovers, allowing organizations to remediate them before they are exploited.
Web Application Hijack Susceptibility: ThreatNG assesses the susceptibility of web applications to hijacking by analyzing external attack surface and digital risk intelligence, including Domain Intelligence, to identify potential entry points. This helps pinpoint misconfigurations or insecure aspects of web applications hosted on subdomains.
Cyber Risk Exposure: This assessment evaluates various parameters within ThreatNG's Domain Intelligence module, including certificates, subdomain headers, vulnerabilities, and sensitive ports, to determine the level of cyber risk exposure. For example, it can identify subdomains with exposed sensitive ports or known vulnerabilities, which could be entry points for attackers. Code Secret Exposure is also factored in, as ThreatNG discovers code repositories and their exposure levels, investigating their contents for sensitive data. This means if a subdomain is associated with a public code repository containing exposed API keys or credentials, ThreatNG will identify this critical risk.
Breach & Ransomware Susceptibility: This is calculated based on external attack surface and digital risk intelligence, including domain intelligence (exposed sensitive ports, exposed private IPs, and known vulnerabilities), dark web presence (compromised credentials, ransomware events, and gang activity), and sentiment and financial analysis. If a subdomain is linked to a system with known vulnerabilities or if credentials associated with that subdomain have been compromised and found on the dark web, ThreatNG will flag this, indicating a higher susceptibility to breaches and ransomware.
Mobile App Exposure: ThreatNG evaluates how exposed an organization's mobile apps are by discovering them in marketplaces and analyzing their content for access credentials (like Amazon AWS Access Key ID, various API keys, and generic usernames and passwords), security credentials (like PGP private keys and RSA private keys), and platform-specific identifiers (like Admin Directories and exposed S3 Buckets). If a mobile app associated with a subdomain contains hardcoded credentials, ThreatNG will identify this significant risk.
Positive Security Indicators: Beyond just finding vulnerabilities, ThreatNG also identifies and highlights an organization's security strengths, such as the presence of Web Application Firewalls or multi-factor authentication, validating their effectiveness from an external attacker's perspective. This provides a more balanced view of the security posture of subdomains.
Reporting: ThreatNG offers a variety of reports, including Executive, Technical, Prioritized (High, Medium, Low, and Informational), Security Ratings (A through F), and Ransomware Susceptibility. These reports provide clear, actionable insights into the security posture of subdomains, allowing organizations to prioritize remediation efforts effectively.
Continuous Monitoring: ThreatNG provides constant monitoring of an organization's external attack surface, digital risk, and security ratings for all organizations. This ensures that any new or emerging vulnerabilities related to subdomains are quickly identified, allowing for prompt action.
Investigation Modules: ThreatNG's investigation modules offer deep dives into various aspects relevant to subdomain security:
Domain Intelligence: This module provides a comprehensive overview of digital presence, including Microsoft Entra Identity and Domain Enumeration, as well as related SwaggerHub instances.
DNS Intelligence: Provides Domain Record Analysis (IP Identification, Vendors and Technology Identification), Domain Name Permutations (Taken and Available), and Web3 Domains (Taken and Available). This is crucial for identifying potential subdomain takeover opportunities.
Subdomain Intelligence: Offers in-depth analysis of subdomains, including HTTP Responses, Header Analysis (Security Headers and Deprecated Headers), Server Headers (Technologies), Cloud Hosting providers (AWS, Microsoft Azure, Google Cloud Platform), Website Builders (Strikingly, Tilda, WordPress), E-commerce Platforms (Bigcartel, Shopify), and Content Management Systems (WordPress). It also identifies content such as Admin Pages, APIs, Development Environments, and VPNs. Furthermore, it details exposed Ports (e.g., IoT/OT, Industrial Control Systems, Databases, Remote Access Services) and Known Vulnerabilities. This enables organizations to view the applications and services running on their subdomains and identify potential vulnerabilities. For example, if a
dev.example.comsubdomain is found with an exposed SSH port and an outdated WordPress version with known vulnerabilities, ThreatNG will highlight this.
Sensitive Code Exposure: This module identifies public code repositories and reveals digital risks, including exposed Access Credentials (various API keys, access tokens, generic usernames, and passwords), Security Credentials (cryptographic keys and private SSH keys), and Configuration Files (application, system, and network configurations). For instance, if
git.example.comIs a public code repository containing an AWS Access Key ID, ThreatNG will detect this critical exposure.Cloud and SaaS Exposure: ThreatNG identifies sanctioned and unsanctioned cloud services, cloud service impersonations, and open-exposed cloud buckets from major providers, including AWS, Microsoft Azure, and Google Cloud Platform. It also identifies various SaaS implementations such as Salesforce, Slack, and ServiceNow. If a subdomain is linked to an openly accessible AWS S3 bucket, ThreatNG will flag this as a significant data leak risk.
Search Engine Exploitation: This helps users investigate an organization’s susceptibility to exposing sensitive information via search engines, including errors, sensitive data, and vulnerable files. This can reveal inadvertently exposed sensitive data or configurations on subdomains.
Intelligence Repositories (DarCache): ThreatNG's continuously updated intelligence repositories provide vital context:
DarCache Vulnerability: This includes NVD (National Vulnerability Database) information with details on attack complexity, impact scores, and CVSS scores. It also incorporates EPSS (Exploit Prediction Scoring System) data, providing a probabilistic estimate of the likelihood that a vulnerability will be exploited. Furthermore, it includes KEV (Known Exploited Vulnerabilities) that are actively being exploited in the wild, and Verified Proof-of-Concept (PoC) exploits directly linked to known vulnerabilities. This allows ThreatNG to not only identify vulnerabilities on subdomains but also to prioritize those that are most likely to be weaponized.
DarCache Dark Web, Compromised Credentials (DarCache Rupture), and Ransomware Groups and Activities (DarCache Ransomware): These repositories provide information on compromised credentials and ransomware events. If credentials associated with a subdomain are found on the dark web, ThreatNG will identify this, indicating a direct threat.
Working with Complementary Solutions:
ThreatNG's unauthenticated, outside-in approach complements internal security solutions, such as Endpoint Detection and Response (EDR) or Security Information and Event Management (SIEM) systems. While internal tools focus on threats within the network, ThreatNG provides the external perspective, identifying weaknesses before an attacker gains entry.
Examples of ThreatNG Helping:
Preventing Subdomain Takeovers: An organization discovers through ThreatNG's Subdomain Takeover Susceptibility assessment that
oldblog.example.comis pointing to a deprovisioned WordPress VIP instance. ThreatNG highlights this dangling DNS record, allowing the security team to remove it before an attacker can claim the subdomain and host a phishing site.Identifying Exposed Development Environments: ThreatNG's Subdomain Intelligence module identifies
dev.example.comas an exposed development environment with an open SSH port and an unpatched Jenkins instance. This critical finding, along with a link to a known Jenkins vulnerability in DarCache Vulnerability, prompts the development team to secure the environment and patch the software immediately.Detecting Leaked Credentials: Through its Sensitive Code Exposure module, ThreatNG finds a public GitHub repository linked to
internalapp.example.comthat contains an exposed AWS Access Key ID. The DarCache Rupture (Compromised Credentials) repository further confirms that these credentials have been seen on the dark web. This allows the organization to revoke the compromised key and rotate all associated credentials, preventing a potential cloud breach.
Examples of ThreatNG Working with Complementary Solutions:
ThreatNG + SIEM: ThreatNG identifies a high-risk subdomain with an exposed admin panel. This information is fed into the organization's SIEM system. If the SIEM then detects unusual login attempts or suspicious activity originating from that subdomain, the combined intelligence allows for a faster and more informed incident response.
ThreatNG + Vulnerability Management Solution: ThreatNG's External Assessment identifies several critical vulnerabilities on a publicly accessible subdomain. This information is then integrated into the existing vulnerability management solution, creating tickets for the security team to prioritize and remediate, ensuring that external risks are incorporated into the internal remediation workflow.
ThreatNG + Incident Response Playbooks: When ThreatNG detects a potential subdomain takeover or a significant data exposure on a subdomain, it can trigger automated alerts that align with an organization's existing incident response playbooks. This ensures a rapid and coordinated response to external threats, leveraging the detailed findings from ThreatNG's investigation modules.
