Maltrail is a production-grade malicious traffic detection system that monitors network traffic in real-time, matching against a dynamic set of threat indicators (trails) and applying behavioral heuristics. It consists of two main components: a high-performance Rust sensor for packet capture and analysis, and a Python server for event intake, web dashboard, and API. The sensor uses libpcap for live capture or offline pcap replay, parses protocols (DNS, HTTP, TLS, QUIC), and performs trail matching and heuristic detection (port scanning, beaconing, DNS tunneling/exhaustion). Events are sent to the server via UDP or stored locally. The server provides a web UI for visualization, search, and management, supports remote logging to SIEMs (syslog, CEF, Logstash), and exposes a REST API for integration. The architecture is modular: the sensor is a multi-threaded Rust binary with lock-free metrics, memory-mapped trail stores, and fuzz-tested protocol parsers. The Python server handles configuration, trail updates from 40+ threat feeds, event logging, and the web interface. The system is designed for scalability with multi-worker capture, bounded memory heuristics, and efficient data structures (LRU caches, interned strings, hash tables). External dependencies include libpcap, SQLite, and various threat feed sources. The codebase demonstrates high craftsmanship with extensive testing (unit, integration, fuzz, parity tests between Rust and Python), CI/CD pipelines, and Docker/systemd deployment support.