Network sniffing is the practice of intercepting and logging traffic passing over a network. Ethical hackers use packet sniffers like Wireshark to monitor networks for:
Plaintext credentials – Sniffing can detect login details, session cookies and other sensitive info transmitted in cleartext.
Activity patterns – Traffic volumes and packet contents reveal system behaviors, popular services etc.
Protocol weaknesses – Analyzing traffic can uncover flaws and bugs in networked applications and services.
Hidden clients – Sniffing can also detect unauthorized clients, bots and other anomalies on the network.
By essentially eavesdropping on all network communications, sniffing provides invaluable intelligence for hackers mapping out targets.