Although I am not sure whether this has been seen in the wild yet, there are some security experts in the UK who are going to
demonstrate a security exploit for WiFi networks called the "Evil Twin" at an educational seminar in London. The essence of the Evil Twin attack is that you go into (for example) a Starbucks and you want to make your WiFi connection so you can surf the Internet. Little do you know, someone is sitting outside in a car with a different access point designed to jam the signal of the T-Mobile access point and instead replace the signal with its own. As part of the scam, a login screen matching that of the normal provider would appear on your Pocket PC or notebook. You would use your legitimate login/password to get into the system and access the Internet - but what you may not know, is that the page is set up to relay your information back to the criminal along with other personal data and information.
'Professor Brian Collins, head of Cranfield's Information Systems Department, said the dangers will only increase as hot spots become more common. However, like other wireless security experts, he said users can mitigate most problems simply by turning security measures on. Most wireless laptops ship with security deactivated.
The popularity of Intel Corp.'s Centrino chip for wireless laptops has played a big part in popularizing Wi-Fi, according to industry observers. Intel this week introduced a new Centrino with additional wireless security features, including built-in support for Cisco-compatible extensions for WPA (Wi-Fi Protected Access).'
Not sure how the average every day WiFi user would know whether they are logging in to a correct base station or not...