Clumsy is a Windows network fault injection tool that intercepts system-wide network traffic at the kernel level using the WinDivert driver, without requiring proxy configuration or application code changes. It captures and manipulates packets for all running applications, including localhost connections, enabling controlled testing of application behavior under degraded network conditions.
The tool provides comprehensive network impairment capabilities including latency simulation, bandwidth throttling, packet loss, corruption, duplication, and reordering. Users can apply these impairments selectively by packet direction (inbound, outbound, or loopback) and filter traffic using logical expressions based on protocol, port, or IP address. Real-time interactive controls allow starting and stopping packet manipulation on demand with live visual feedback while applications continue running.
Clumsy supports randomized packet mutation that can simultaneously drop, duplicate, or corrupt a configurable percentage of packets to emulate network degradation. An in-memory packet buffer holds intercepted packets to introduce latency, reorder traffic, or throttle throughput before forwarding. The tool is available as a Windows executable that can be run without installation.
