Wireshark

The book I read to research this post was Practical Packet Analysis by Chris Sanders which is a very good & an excellent introduction to wireshark. I bought it from kindle. Many of the tools that help you secure a network also play a part if you want to hack, that's a fact of life. I'm just going to do a general introduction to wireshark & the associated programs that help with wireless security. Wireshark is an open source packet sniffer although if you do a search for it in google you will find certain dubious types trying to sell it. Get the free version, I think if you do a search for snake oil there's also people selling that. Basically wireshark tells you where your data is going & don't forget although data may only be read by one computer on a network, chances are it's sent but not read by every other computer on the network. You need a proper hub on your network to read the packets & don't forget many so called hubs are in fact low level switches which aren't suitable for this purpose. Chances are if you get a proper hub it'll be a secondhand one which you may get quite cheap. Nmap is used to tell you what's on the network which you should already know if you are a network administrator. Wireshark will only scan one channel but kismet is quite useful it'll scan 10 channels per second. Finally another thing you might be interested in is cloudshark which is a cloud or online version of wireshark.