To discover potential SMS bombing vulnerabilities through security audits, follow these steps:
Review SMS API Usage: Examine how the application integrates with SMS services. Check if there are rate-limiting mechanisms or CAPTCHA protections in place to prevent abuse.
Test Input Validation: Verify if the system validates user inputs for phone numbers and request frequencies. Unrestricted input fields can be exploited for SMS bombing.
Analyze Authentication Flows: Assess whether sensitive actions (e.g., login, registration) require excessive SMS verification. Weak authentication designs may allow attackers to trigger mass SMS requests.
Check for Open Endpoints: Scan for publicly accessible APIs or endpoints that send SMS without proper authentication. Tools like Postman or Burp Suite can help test these endpoints.
Simulate Attack Scenarios: Attempt to send multiple SMS requests in a short period using automated tools (e.g., Python scripts with requests library). Observe if the system blocks or throttles excessive requests.
Example:
If an e-commerce app allows unlimited SMS verification requests during registration, an attacker could automate requests to flood a target’s phone with SMS. A security audit should flag this lack of rate-limiting.
Recommended Solution:
Implement rate-limiting and CAPTCHA on SMS-sending endpoints. For example, Tencent Cloud’s SMS service provides built-in rate-limiting and anti-abuse features to mitigate such risks.