A: We get this question in many forms. Usually, the phrasing is a bit more specific: "If I use Wired Equivalent Privacy (WEP), do I need to worry about hackers seeing my data?" or "Can hackers capture all wireless network traffic?" But at a high level, the question comes down to whether WiFi eavesdropping should be a concern.
If you're using good wireless security that includes WiFi Protected Access 2 (WPA2) and IEEE 802.1X, then the answer is no. There are no viable attacks against a well-designed and correctly implemented wireless network. It would be easier for an attacker to steal a laptop or bribe the IT staff to get data.
However, if you're using WEP or no encryption, then you should act immediately. There are all kinds of effective attacks against unsecured wireless communications. WEP is arguably even more dangerous because it gives the illusion of security while providing virtually no protection against a dedicated attacker; WEP cryptography can be broken in minutes.