Wireshark is a leading open-source penetration testing tool used for network protocol analyzers. It uses packet sniffing and API to capture the data packets. It also captures the VoIP data packets or calls made across the network, thus allowing the user access to the data. Besides this, it provides offline analysis of the live capture of the data packets, ensuring that Wireshark delivers the most authentic test results. This cross-platform tool works on various operating systems such as Windows, Linux, Solaris, and macOS; you can download it for free.