Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
SelfishNet - Block anyone or any device from using your internet
Angry IP Scanner - Open-source and cross-platform network scanner designed to be fast and simple to use
Wifi Router Manager - Wifi Router Manager is a free-to-use network tool application that is providing the complete visibility of your wifi network from signal strength, security to IP addresses.
Fing - Discover which devices are connected to any Wi-Fi network, map devices, detect intruders, assess...
SoftPerfect WiFi Guard - Security of your Wi-Fi network for Windows, macOS and Linux