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If a network has been compromised (e.g. someone is listening on the traffic or there has been malware implemented on it), is it safe to leave a device (PC, cell phone, gaming device, etc.) in range of the network, as long as you don't connect to it? Should I disable WiFi when I don't need it to avoid this risk?

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    People can listen to devices searching for networks and determine what networks a device would automatically connect to, then create that network. – Grant Garrison Jun 25 at 5:45
  • Could the devices remain untouched if they did not connect to any network? – user210868 Jun 25 at 5:47
  • Check out WiFi pineapple and an attack using it. If the device is allowed to connect to a network, which basically means WiFi isn’t turned off, the device could be vulnerable. – Grant Garrison Jun 25 at 5:50
  • Alright, thanks very much. I've looked at the Pineapple and what I've seen is that it basically creates an identical network to a nearby one. Could you stay clear of a Pineapple attack if your device did not have any stored networks? What if the only nearby networks are secure networks (though still compromised)? – user210868 Jun 25 at 5:59
  • If your device is set to not automatically connect to known networks, you should be good, but this could be difficult. Nearly every device attempts to automatically connect to known networks and turning it off may be difficult on some devices. Plus, not connecting to known networks is a real hassle. I’m not 100% sure if the WiFi pineapple can create secured networks, but I’m if you only have secure networks that would automatically connect, you might be ok. – Grant Garrison Jun 25 at 6:22
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If your device isn't connected to the network, either because WiFi is turned off or because your device isn't configured to automatically connect to the network, nothing on that network can affect your device.

However, an attacker may create a network with the same SSID and PSK as one that your device recognizes, such as the WiFi network used at your workplace. Your device will likely connect automatically in that situation.

To mitigate this risk, assume all networks have something listening, even if it is just the router itself. Make sure all your network traffic is encrypted using a VPN.

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In short, there is no risk when your device is not connected to the network unless the hacker changes the SSID and password of the WiFi to one of the saved (and enabled auto-connect) ones in your device; which is rare, especially when the hacker has not targeted you.

But to be on the safe side:

  • forget (remove) all saved WiFi on your device,
  • use VPN for any sensitive activity, e.g. banking stuff,
  • be sure about certificates; using Chrome or Firefox will assure you fairly if it is forged or not,
  • Having some tools like antivirus and firewall may help.
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Generally, scanning for WiFi networks is done passively by your device. This means that a router broadcasts information (such as the name of the network, authentication method etc.) and your device listens. These networks show up in a list which you can chose to connect to, but the router does not know your device is there until it tries to connect. So being in the area of a compromised network will not affect your device.

Someone could spoof a network you are trying to connect to, but they cannot read a list of networks your device likes to connect to and spoof them. They would have to spoof a nearby network, guessing that you will want connect to it. The authentication protocol should then stop you connecting to the spoofed network. Unless the network doesn't have one, in which case you should not set it to connect automatically and use a VPN.

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    scanning for WiFi networks is done passively by your device: no, it's done actively. The device sends out a request for networks they know. Keep airodump-ng running around your phone and disconnect from your home wifi, you will see the phone asking SSIDs around... – ThoriumBR Jun 26 at 9:40
  • @ThoriumBR My understanding is that there are two types of scanning, passive and active (polling). I beleive that most devices scan passively becuase it is more energy efficient and there is no need to poll networks when they are broadcasting their information. I have found it hard to find good sources detailing the exact procedure though, so if you have a source I'd be interested to read it. – TJK Jun 26 at 10:22
  • On crc.id.au/tracking-people-via-wifi-even-when-not-connected it's explained why active scanning is better for battery: you ask only for known SSIDs, not scan all the channels for all possible SSIDs. – ThoriumBR Jun 26 at 12:03

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