Wireshark is a popular open source network analyzer software that allows users to capture and analyze packets on a network. It can be used for troubleshooting network problems, monitoring traffic levels, and learning about network protocols. Wireshark provides a GUI that allows users to observe all network packets, apply filters, and gather statistics. It supports live packet capture and can import/export pcap files. While useful for monitoring networks, Wireshark is limited in that it does not actively detect intrusions or manipulate network traffic.