In January last year, a hackernetwork that claimed to be based in Saudi Arabia paralyzed the websites of Israel's stock exchange and national airline and claimed to have published details of thousands of Israeli credit cards.
Only, the wireless network you signed into was not only unsecure, it was a decoy network setup by a malicious hacker targeting people casually checking email, like you.
In a talk at the Black Hat security conference in Barcelona Thursday, Greek researcher Thanassis Giannetsos plans to present a new software tool that he and two colleagues have written that they say would allow a malicious hacker to penetrate a sensor network and change or delete data at will.