Mobile Users and Personal Devices
For WiFi access my smartphone supports all the same methods as my laptop for wireless access, so I feel secure using my phone and laptop to access my own private Wlan around the home. (It's NOT a notebook, it's 16 inches wide)
Internal Corporate environments are also usually quite secure, although I recently worked at a site that only has a 40 bit access key and some 200 laptops accessing it, statistically that makes it a weak point for traffic sniffing, especially with just one AP and one Channel.
For other Wlan's I have to rely on the setup of the security for that access point, that's no different than going to Starbucks or other Wlan with minimal protection.
To increase my level of security I ALWAYS use a VPN solution on the more public wireless AP's, and also all Hotel connections ( even Cable connections ), the initial connection is reasonably open, but then I fire up my VPN and everything goes through that. My Smartphone also has VPN support, so I do exactly the same with that.
I know there are sniffers for wireless traffic that can decrypt streams of data and produce a key for access to the Wlan, but as Wlan security levels and methods increase, there are less and less of these tools available.
Corporate access from outside the company always relies on a VPN or other secure tunnel method, if your Phone or PDA doesn't support this, then DON"T DO IT .
I am continually amazed at how many open WLAN's my phone spots as I walk around places, even in countries with paranoia controls on internet access.
I have worked at sites that have a closed policy on their Wlan, and I have seen employee's connecting their PDA/phone through Bluetooth and sharing the IP connection, well, it works, it's easy to set up, but Bluetooth just doesn't have the same security levels as a Wlan, so that's a possible point of attack. Bluetooth power levels are not so high, so any access would probably have to be made in close proximity.
MAC address can be spoofed very easily, so slotting permitted MAC addresses into routers isn't always as secure as people think...
There is plenty to read on the net about security of this nature, so next time you have time to spare, go have a read...