<p>I would like to mention that all of the answers so far are very good tools, as I use them all myself and they are great. A few caveats I'd like to mention though....</p>
<p>1) You need a wifi card that can go into Promiscuous Mode to use aircrack-ng. I suggest an Atheros with the 512 or 512A chipset. There is a list available of compatible cards, but remember that wireless on Linux can be flakey at times, so don't rule that out of aircrack-ng doesn't work right away. Remember, ndiswrapper can be your friend.</p>
<p>2) The greatest weakness of security can also be it's greatest strength, and that is the end-user. Security is not a piece of software, hardware or a setting... it is a mindset. It is a way of thinking, being, and acting 24/7/365. All the network security in the World is useless if people can be social engineered or if physical security is ignored. If your network is secure, but someone steals your hard drive.... well, you get the idea.</p>
<p>I know your post is for tools to use to diagnose your network security, but to simply list the tools, and even how to configure and use them is only giving you PART of the answer. Your goal is beyond what tools to use, your real question and real goal is: "How do I properly assess and secure my network?"</p>
<p>If you have Adobe flash installed, that's a risk.
If you have a . in your PATH, that is a security risk.
If you login as root, that's a risk.</p>
<p>3) Wireless is not really able to be secured compared to wired.
Nothing is 100% secure, so it's a matter of layers/depth of security.</p>
