tcpdump is an open-source packet capture tool that uses the libpcap library to capture network traffic on Linux and Mac OS X operating systems. It can display the contents of packets in various formats, filter packets based on criteria, and save packets to a file. tcpdump is a command-line tool that can be run on a terminal or a remote shell1 References: Understanding Cisco Cybersecurity Operations Fundamentals (CBROPS) - Module 2: Security Monitoring