SpyGuard is a network traffic analysis tool designed for detecting signs of compromise, particularly stalkerware and spyware, by monitoring WiFi traffic from connected devices. It consists of a frontend Vue.js 3 application for user interaction and capture initiation, and a backend Flask API for managing configuration, threat intelligence, and analysis. The core analysis engine processes PCAP files using Suricata, checks traffic against IOC databases and whitelists, performs heuristic and active checks (passive DNS, WHOIS, SSL validation), and generates JSON/PDF reports. External watchers periodically update threat intelligence feeds from sources like Cisco Umbrella and IP-to-ASN mappings. The architecture separates concerns: frontend handles capture UI and device management, backend provides authenticated APIs for system administration, and the analysis engine performs the detection logic. Key entry points include server/frontend/main.py (frontend service), server/backend/main.py (backend API), server/backend/watchers.py (threat intelligence updater), and analysis/analysis.py (analysis trigger).