How do I know if someone is 'piggybacking' off my network? When I select my wi-fi network I see two old network names of mine show up. One is unlocked.
Check the MAC addresses against the MAC addresses of the devices you know are supposed to be on the network.
Typically you can tell by logging into your router. If you have our Cisco modem with the internal router for example, you can log in (192.168.0.1 in your web browser - username cusadmin and password on the modem itself), click Setup at the top then LAN Setup and select Connected Devices Summary.
If you don't see anything listed in there that you don't recognize/own, then it's possible that it could be someone else connected to your network.
The easiest way to prevent this would simply be to change your wireless access password and ensure that you've got WPA2 encryption enabled.
If you need further information on this, just let us know.
You're looking at the list of wireless connections on your computer, and you see your old ones?
Likely your computer still has them saved, but they aren't active, or in use, they are just memorized.
Do a fresh scan for wireless networks to see what you see, and you can remove the old ones, or all of them for that matter, then re-scan and readd the ones you need.
Confirming in the process, that it asks for a password when connecting
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