Almost all of us have jumped onto someone else's unsecured Wi-Fi network. There's little harm in that if you're just an honest soul looking for an Internet connection.
But if you're the owner of an unsecured network, you should be aware that the world's not made up entirely of honest souls--and it's not hard for the dishonest ones to see exactly what you're doing on your network. Sound scary? Here's how to fix the problem.
Q. What are WEP and WPA encryption, and which should I use?
The first line of defense for your Wi-Fi network is encryption, which encodes the data transmitted between your PC and your wireless router. Unfortunately, most routers ship with encryption turned off, and many users don't turn it on, leaving themselves completely exposed. If you haven't already, enable your router's encryption, and use the strongest form supported by your network. The Wireless Protected Access (WPA) protocol and more recent WPA2 have supplanted the older and less-secure Wireless Encryption Protocol (WEP).
Go with WPA or WPA2 if at all possible, since WEP is relatively easy to crack. (You have to use the same form on all devices on your network; you can't mix WEP and WPA.) The keys used by WPA and WPA2 change dynamically, which make them nearly impossible to hack. Use a strong password for your encryption key, such as a combination of letters and numbers of 14 characters or more.
If you have an older router that supports WEP only, you'll be safest if you use 128-bit WEP keys--but also check the manufacturer's Web site for a firmware update that will add WPA support. If it doesn't look like an update is likely, consider replacing old adapters and routers with newer models that support WPA. Look for a router that supports the hybrid WPA + WPA2 mode, which lets you use the stronger WPA2 encryption with adapters that support it, while still maintaining compatibility with WPA adapters.
Make sure you change the default network name and password on your router. Doing so will make it much more difficult for hackers to break into your router and commandeer its settings.