Wireshark is the world's foremost network protocol analyzer. It lets you capture and interactively browse the traffic running on a computer network. It is the de facto (and often de jure) standard across many industries and educational institutions.

Portmaster is a free and open-source privacy suite that puts you back in charge of your computer.

Simple tool to configure Windows Filtering Platform (WFP) which can configure network activity on your computer.

A free, powerful, multi-purpose tool that helps you monitor system resources, debug software and detect malware.

Nmap ("Network Mapper") is a free and open source (license) utility for network exploration or security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or...

Open-source and cross-platform network scanner designed to be fast and simple to use.

A free, powerful, multi-purpose tool that helps you monitor system resources, debug software and detect malware. Official successor to Process Hacker.

Fing helps you understand most of your home network. See all the devices connected to your Wi-Fi, run network scanners, monitor your Internet speed, know your security level, set automated vulnerability checks, and much more.

Gather and analyze accurate statistics and performance metrics, visualize it, get notified about current and potential issues without delay, and take advantage of our time-tested professional development and support.

Visualize network activity in detail, get notified when new apps access the network, look out for malware, and block badly behaving apps.

TrafficMonitor is a network monitoring suspension window software in Windows. It can display the current network speed, CPU and memory usage. It also support the functions of display in the taskbar, change skin and historical traffic statistics.

Simple firewall for MS Windows.

A firewall protects your computer against unwanted guests from the Internet. But who protects your private data from being sent out? Little Snitch does!

Resource monitor that shows usage and stats for processor, memory, disks, network and processes.

Zenmap is the official cross-platform GUI for the Nmap Security Scanner. It is free and runs on Linux, Windows, Mac OS X, etc. Zenmap aims to make Nmap easy for beginners to use while providing advanced features for experienced Nmap users.