Do you always turn WiFi off on your smartphone before leaving the house or work? You might think there's no harm in having WiFi turned on but not connected to a network, but that's not necessarily the case.
A wireless device goes through a discovery process in which it attempts to connect to an available wireless network. This may either be ‘passive’ - listening for networks which are broadcasting themselves - or ‘active’ - sending out probe request packets in search of a network to connect to.
Most devices use both passive and active discovery in an attempt to connect to known/preferred networks. So it's very likely that your smartphone is broadcasting the names (SSIDs) of your favourite networks for anyone to see.
===> An ‘evil twin’ attack could even accomplish this without needing any knowledge of your WiFi password - very damaging for all of those who use mobile banking for instance! <===
Gust MEES: a MUST READ for anyone using m-Learning + "BYOD" and also any smartphone user...
http://nakedsecurity.sophos.com/2012/10/02/what-is-your-phone-saying-behind-your-back/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+nakedsecurity+%28Naked+Security+-+Sophos%29
one of interesting information, the video shows the security risk in daily life using smart phone. It is easy to call public to aware about the mobile security, also it contains lots of data which are useful