KRACK attack (Key Reinstallation Attack) works against almost any WPA2 Wi-Fi network. Attack allows attackers to decrypt WiFi users data without cracking or knowing the password. KRACK Detector is a Python script to detect possible KRACK attacks against client devices on your network. The tool is available on Github at Github at the end of the month and is free to download from the source of the tool. It listens for duplicate message 3 of the 4-way handshake and disconnects the suspected device, preventing it from sending any further sensitive data to the Access Point.”]
Source: http://securityaffairs.co/wordpress/65229/hacking/krack-detector.html