A packet sniffer is a tool used to monitor and analyze network traffic. It captures data packets that travel across a network, allowing users to see the information being sent and received. This can help in troubleshooting network issues, monitoring performance, and ensuring security by detecting unauthorized access. Packet sniffers can be both hardware and software-based. They are commonly used by network administrators and cybersecurity professionals to understand network behavior and identify potential vulnerabilities. However, they can also be misused by malicious actors to intercept sensitive information, making it important to secure networks against unauthorized sniffing.