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Threat Model Analysis for librespeed/speedtest

Threat: Denial of Service (DoS) via Repeated Requests

  • Description: An attacker sends a large number of speed test requests in a short period, either from a single IP address or distributed across multiple IP addresses (DDoS). This overwhelms the server's resources (bandwidth, CPU, memory) specifically allocated to handling the speed test functionality. The attacker exploits the intended functionality of the speed test to cause a denial of service.
    • Impact: The server becomes slow or unresponsive, preventing legitimate users from performing speed tests. This directly impacts the availability of the speed test service and potentially other application features if resources are shared. Could lead to a complete service outage.
    • Affected Component: The entire server-side infrastructure handling the speed test requests. This includes the backend code that processes the incoming data and the network infrastructure itself. Specifically, LibreSpeed files like empty.php, getIP.php, etc. (if using the PHP backend), which are the entry points for handling speed test data, are directly targeted.
    • Risk Severity: High (Can directly impact service availability, and the speed test is the intended vector of attack).
    • Mitigation Strategies:
      • Strict Rate Limiting (Essential): Implement robust rate limiting per IP address and globally. Limit the number of speed tests allowed within a defined time window. This is the primary defense.
      • Resource Monitoring: Continuously monitor server resources (CPU, bandwidth, memory) to detect and respond to DoS attacks targeting the speed test functionality.
      • Web Application Firewall (WAF): Employ a WAF to identify and block malicious traffic patterns characteristic of DoS attacks aimed at the speed test endpoints.
      • CAPTCHA (If Necessary, but User-Experience Impact): Consider adding a CAPTCHA before initiating a speed test to deter automated attacks, but carefully weigh this against the impact on user experience.
      • Backend Optimization: Optimize the backend code that handles speed test requests to be as efficient as possible, minimizing resource consumption per request. This increases the threshold for a successful DoS attack.

Threat: Server Resource Exhaustion via Large Uploads/Downloads (Specific DoS Variant)

  • Description: Even with rate limiting on request frequency, an attacker could exploit the speed test's core functionality by initiating tests with very large upload or download sizes (within the configured limits of LibreSpeed, if those limits are too permissive). This focuses on consuming bandwidth, a key resource used by the speed test.
    • Impact: Degraded performance for other users attempting to use the speed test or other services sharing the same bandwidth. Potentially increased bandwidth costs for the server operator. Could lead to a denial of service if bandwidth is completely saturated.
    • Affected Component: Server-side components directly responsible for handling the upload and download data streams during the speed test. This includes files like empty.php in the PHP backend (which handles data reception), and the web server itself (which manages the network connections).
    • Risk Severity: High (Directly exploits the intended function of the speed test to cause resource exhaustion).
    • Mitigation Strategies:
      • Configure Reasonable Limits (Crucial): Set strict and reasonable limits within the LibreSpeed configuration for the maximum upload and download sizes and durations. These limits should be carefully chosen to balance functionality with security.
      • Bandwidth Monitoring: Implement continuous monitoring of bandwidth usage, with alerts for unusually high consumption specifically related to the speed test endpoints.
      • Traffic Shaping (Advanced): Consider using traffic shaping techniques (at the network or application level) to limit the bandwidth allocated to individual speed test sessions, preventing any single session from monopolizing resources. This is a more sophisticated mitigation.