Well a sniffer is something completely different. That's why with wireless you should always use a VPN.

Take our setup for instance. We have a DSL connection to the internet, All wireless users have Internet access to start, but if they want to acces the corporate net they must install the VPN client to tunnel back through tthe internet to our VPN gate. Of course I'm simplifying ever so slightly but you get the jist of the concept.

Always treat wireless as suspect, never trust it.