Tool · IT, Security

Wireshark

Capturing packets and decoding them field by field, Wireshark shows exactly what crosses a network, protocol by protocol. Network engineers troubleshoot with it, security analysts investigate suspicious traffic, and students use it to see what textbook protocols really look like. It is free and open source. Capturing is easy; knowing where to look is the skill, since a busy link produces far more packets than anyone can read.

Maker's site: www.wireshark.org (opens in a new tab) (no commission).