Wireshark is a free open source tool that analyzes network traffic in real-time for Windows, Mac, Unix, and Linux systems. It captures data packets passing through a network interface (such as Ethernet, LAN, or SDRs) and translates that data into valuable information for IT professionals and cybersecurity teams. Wireshark is a type of packet sniffer (also known as a network protocol analyzer, protocol analyzer, and network analyzer).
Wireshark (formerly known as ethereal) offers a series of different display filters to transform each captured packet into a readable format.
Because you can download Wireshark for free, cybercriminals have liberal access to it, so it's best security practice to assume the software is currently being used with hostile intentions.