Fox IO is a cybersecurity company focused on network traffic fingerprinting and threat detection through its JA4+ suite of open standards. The company develops and maintains JA4+ — a collection of 12+ protocol-layer fingerprinting methods designed to identify and analyze network connections without requiring client-side JavaScript. Core fingerprinting methods include: - JA4: TLS client fingerprinting - JA4S: TLS server response/session fingerprinting - JA4H: HTTP client fingerprinting - JA4L/JA4LS: Client and server latency/light distance measurement - JA4X: X.509 TLS certificate fingerprinting - JA4SSH: SSH traffic fingerprinting - JA4T/JA4TS: TCP client and server response fingerprinting The technology operates at the protocol layer, analyzing connection behavior rather than relying on application-layer signals. This approach enables detection of bots, proxies, VPNs, malware, command-and-control (C2) infrastructure, credential stuffing, session hijacking, and rogue devices — including in environments where JavaScript is unavailable, such as APIs, mobile apps, IoT, and SCADA/OT systems. Fox IO also offers patent-pending technology for estimating real client geolocation behind proxies and VPNs. The JA4+ libraries and SDKs integrate natively with platforms such as Zeek, Suricata, and major SIEM and cloud providers. Beyond the open fingerprinting standards, the company is building a broader traffic intelligence platform that adds detection automation and enterprise integrations. Noted enterprise users include Walmart, Amazon, and McKesson. The company targets security engineering teams and enterprise security operations.