API Security Assessment

An API security assessment is a systematic, structured process for evaluating the security posture, compliance, and overall resilience of Application Programming Interfaces (APIs) against cyber threats. Unlike traditional security audits, which may focus only on application perimeters, API assessment targets the unique vulnerabilities introduced by the data-sharing interfaces between disparate software components.

Core Components of an API Security Assessment

A practical API security assessment encompasses several critical areas designed to find weaknesses across the entire API lifecycle.

1. Discovery and Inventory

The assessment must begin by discovering and cataloging all APIs within an organization. This includes officially documented APIs, shadow APIs (unknown or undocumented), third-party integrations, and zombie APIs (deprecated but still running versions). Without a complete inventory, security efforts will have blind spots.

2. Vulnerability and Risk Analysis

This step involves a deep technical evaluation to identify, exploit, and prioritize security flaws. It typically focuses on the OWASP API Security Top 10 risks.

• Authentication Testing: Verifying that the mechanisms used to confirm a user's identity (e.g., tokens, API keys, multi-factor authentication) are robust and cannot be easily bypassed. Testing involves trying requests with missing, expired, or invalid tokens.

• Authorization Testing: Ensuring that authenticated users can only access the resources and functionalities they are specifically allowed to use. This is crucial for preventing flaws such as Broken Object-Level Authorization (BOLA) and Broken Function-Level Authorization, in which an attacker manipulates parameters to access unauthorized data.

• Input Validation Testing: Checking every piece of data submitted to the API to prevent injection attacks (like SQL injection or command injection) by ensuring the data conforms to expected formats, types, and ranges.

• Business Logic Testing: Manually testing the unique workflows and logic of the API to find complex flaws that automated tools might miss, such as manipulating a multi-step process for unauthorized gains.

• Sensitive Data Exposure: Verifying that the API does not unnecessarily return large or sensitive datasets in response to simple queries, which is often a default setting (Excessive Data Exposure).

• Configuration Review: Testing the security configuration of the API gateway, Web Application Firewall (WAF), and underlying servers to ensure no default or insecure settings are left exposed.

3. Assessment Methodologies

Assessments are generally conducted using a combination of methods:

• Static Application Security Testing (SAST): Analyzing the API's source code without executing it to find hardcoded secrets, insecure coding patterns, and configuration errors. This is performed early in the development lifecycle (shifting left).

• Dynamic Application Security Testing (DAST) / Penetration Testing: Interacting with the running API from the outside by sending various payloads and requests to simulate an attacker. This includes fuzzing, where random or unexpected data is sent to uncover coding errors.

• Software Composition Analysis (SCA): Scanning the API's third-party components and open-source libraries for known vulnerabilities.

4. Continuous Monitoring and Compliance

API security is dynamic and requires continuous vigilance.

• Real-time Monitoring: Implementing solutions to monitor API traffic and behavior for anomalous traffic patterns or suspicious activities that could indicate an attack or abuse.

• Compliance Checks: Verifying that the API's security controls and data handling procedures adhere to relevant regulations like GDPR or HIPAA.

ThreatNG provides a powerful, agentless approach to API security assessment by focusing on the external, attacker-centric view of an organization's API attack surface. It addresses key assessment stages—discovery, vulnerability analysis, and continuous monitoring—without requiring internal access or credentials.

ThreatNG's Role in API Security Assessment

External Discovery and Continuous Monitoring

ThreatNG’s core capability is purely external unauthenticated discovery, which is the foundational step of any API security assessment: Discovery and Inventory. It simulates an attacker's reconnaissance to identify all publicly exposed APIs, including potential shadow APIs or deprecated zombie APIs that might not be in the official inventory. This discovery is then maintained through Continuous Monitoring of the external attack surface, ensuring that if a new, unsecured API is deployed, the assessment remains up to date.

External Assessment and Examples

ThreatNG performs numerous external assessments that directly map to finding vulnerabilities in APIs:

• Cyber Risk Exposure: This rating identifies direct security gaps on API-hosting infrastructure. It reports on Subdomains intelligence, which includes:

• Exposed Ports: Direct exposure of services that might be API backends. Example: ThreatNG detects an exposed MongoDB database port or Redis port on a subdomain, indicating an unauthenticated path to an API's backend data store.

• Missing Headers: Lack of security controls, such as Content-Security-Policy or HSTS, on subdomains that host APIs.

• Data Leak Susceptibility: This rating identifies external digital risks, such as Compromised Credentials and Known Vulnerabilities, down to the subdomain level.

• Example: An exposed API running on a subdomain with a known vulnerability (CVE) that ThreatNG flags contributes to the data leak risk.

• Mobile App Exposure: This assessment evaluates how exposed an organization’s mobile apps are, specifically looking for Access Credentials like API Keys and Authorization Bearer tokens.

• Example: ThreatNG finds a hardcoded Stripe API Key or Google API Key within the publicly available mobile application files, which is a severe API security flaw.

Investigation Modules and Examples

The investigation modules provide the detailed, technical evidence that fuels the assessment:

• Sensitive Code Exposure: This module is critical for detecting API Key Exposure. It uncovers digital risks in public code repositories, including numerous Access Credentials (e.g., Stripe API keys, Google OAuth Keys) and Cloud Credentials (e.g., AWS Secret Access Keys).

• Example: ThreatNG discovers a public GitHub repository containing a configuration file with a leaked MailChimp API Key. This secret could be used to tamper with customer data via the marketing API.

• Subdomain Intelligence: This module performs unauthenticated analysisby checking HTTP Responses and headers for discovered API endpoints. It also checks for Content Identification of APIs on subdomains.

• Domain Intelligence (Domain Overview): This module can identify related SwaggerHub instances that provide API documentation and specifications, enabling security teams to understand the API’s structure and functionality for deeper testing.

• Known Vulnerabilities: ThreatNG externally discovers and assesses for known vulnerabilities by cross-referencing discovered assets and technologies with its intelligence repository, which includes KEV (to confirm active exploitation) and Proof of Concept Exploits. This helps prioritize API vulnerabilities based on real-world exploitability.

Intelligence Repositories and Reporting

• Intelligence Repositories (DarCache): The DarCache Rupture (Compromised Credentials) and DarCache Dark Web repositories provide essential context for exposed API keys. If a key is found in public code (via Sensitive Code Exposure), DarCache checks whether it has been compromised elsewhere and immediately escalates its priority.

• Reporting: The Prioritized Report (High, Medium, Low) assigns technical findings for exposed API endpoints and leaked keys to actionable risk levels. The Security Ratings (A through F) provide a high-level governance metric for the organization's overall API security posture.

Complementary Solutions

ThreatNG's agentless findings can be seamlessly integrated with specialized API security tools to establish a complete assessment and enforcement loop:

• API Gateways: ThreatNG discovers the entire external API inventory, including shadow APIs. This external inventory can be shared with an API Gateway solution. The Gateway can then use this list to automatically onboard previously unknown endpoints and apply mandatory policies, such as rate limiting and strong authentication.

• API Security Testing Tools (e.g., Dynamic Application Security Testing - DAST): ThreatNG’s Domain Intelligence can expose SwaggerHub specifications or unauthenticated endpoints. This structure and inventory information can be fed into a DAST tool, enabling it to perform deeper, automated authentication and authorization testing against a complete, validated list of external API endpoints.

• Security Orchestration, Automation, and Response (SOAR) Platforms: When ThreatNG detects a leaked Stripe API key through the Sensitive Code Exposure module, the high-certainty finding can be automatically sent to a SOAR platform. The SOAR platform can immediately use this alert to trigger a predefined playbook that automatically revokes the compromised key in the Stripe console and notifies the relevant development team.