Certain names are a giveaway that a network probably won’t be password-protected. Look for “linksys,” “default,” “Wireless,” “NETGEAR,” “belkin54g,” and “Apple Network 0273df.” These are the default network names for the most popular wireless routers. If a network owner hasn’t taken the time to change the default name, that’s a good clue that they probably won’t have a password either. You should also look for signs of hacker culture. Since hackers love giving away Net access, an all-lowercase name like “hackdojo” is most likely an invitation to log on. On the other hand, a name in all caps is typically a network under corporate lockdown.
If you do get prompted for a password, try “public”—that’s the default on many of Apple’s AirPort units. You can also try common passwords like “admin,” “password,” and “1234”—or just check out this exhaustive list of default passwords. You should also try using the name of the network in the password space. A generic password could mean that the network’s owner didn’t have the sense to pick something less obvious or that they’ve decided to welcome outsiders. But who cares? You’re in. And again, there’s no specific law barring you from guessing the password, as long as you don’t crack an encrypted network and read other people’s transmissions.