How to View Someone's WiFi Activity

It is much much harder than it sounds. So step 1 is to capture the traffic in the first place. Microsoft thinks putting your head in the sand is a solution to hackers so you need to use a linux install to be able to use the command that puts a wireless nic in promiscuous mode so you can capture all traffic. Not all nics can do this.

So now lets assume you somehow manage to capture all the traffic which tends to be very tough now days with routers sending multiple overlapping wireless signals to increase the speed.

You now must decrypt the traffic. Since you know the pre shared key on your wireless it at least can be done. You must have capture the traffic from the very first packets. The pre shared key is only used to generate the session key. Each person using the wireless is actually using their own keys once things get going. But if you have the start of the session you can get the first session key. You can then decrypt the data watching for the key changes that happen every fixed amount of time or amount of bytes. If you happen to not capture those packets because of some noise or something you will not be able to decrypt traffic until the session is restarted from the beginning.

After all this you can finally try analyze what he is up to.

Maybe a better answer is you can't unless you are very determined.

Now if we talk about file shares and such the machine can see each other but only what is allowed. So if you share files onto the network the other machines can see them. To a point you can prevent even this. There is a option called wireless isolation that prevents wireless devices from communicating on the same router. You can still talk between wired and wireless devices though.

Motoring usage is kinda tough with consumer grade equipment. Some routers have very basic logging but don't have anyplace to store it. You could use third party firmware like dd-wrt and its version of netflow. This keeps track of all the session data and send reports to a external machine for storage and analysis. Other than that you end up having to put a machine in the path. Normally this is some type of firewall that can collect data logs. Placement tends to be a issue because you can not get between the wireless and the router itself. You end up placing it between the router and a modem. At this point though all the data from the users is mixed because of the NAT. The only recommendation I have seen for this is to use the QoS markings to mark each users with different code.

The other way that may work is to use a service like opendns. It really only tells you the DNS queries that are made not what is being done on the site and there really is no way to tell different users apart. It is easily bypassed but I won't post how here but it is trivial.