Privacy@lemmy.mlbycomfy@lemmy.ml
10 hours

On a typical Linux distro, what information do WiFi access points get when you search for and use another AP?

Let’s say, I sit down in a mall, open my laptop and connect to a secured mobile hotspot. Then I do it again next week after a reboot. What information would a nearby shop or a passive malicious hacker be able to find about my device? Does my device send out identifying information before joining, like a MAC address? Is this persistent, or randomized?

I intentionally haven’t specified a distro, so if something only applies to some network managers, give some details.

Bonus points: what about Android phones?

13
    • ApertureUA@lemmy.todayEnglish
      7 minutes

      Most compromised routers scrape the hostname (both regular and mDNS) and MAC address. What you do is disable mDNS related daemons like kdeconnect and avahi (until you want them) and put this in /etc/NetworkManager/NetworkManager.conf:

      [main]
hostname-mode=none

[device]
wifi.scan-rand-mac-address=yes

[connection]
ethernet.cloned-mac-address=random
wifi.cloned-mac-address=random
connection.mdns=0
connection.llmnr=0

      (yes, the mdns bit above is a bit redundant, but systemd has something related that might read it and better be safe than sorry)

      This won’t protect you if the router is a bit smarter and can see your NTP server (usually like “x.archlinux.pool.ntp.org” instead of just “x.pool.ntp.org”), your connectivity check (same as NTP) and other servers your machine connects to (like Tor nodes if you have the daemon running and oftc.net if you have an IRC client). The good news is that none are known to check that (at least to me).

      • kwarg@mander.xyz
        10 minutes

        Is this why my GOS phone does not connect back to my home wifi every time i leave and come back?

      • bob_lemon@feddit.org
        25 minutes

        I hope there’s a whitelist of SSIDs for this. I wouldn’t want my home router to register a new device each time I come back home

        • ApertureUA@lemmy.today
          5 minutes

          It’s a native Android feature since ~9 IIRC. Well, if the ROM maintainer didn’t decide to disable it for whatever reason :(

          You can toggle it off for specific networks.

    • Scipitie@lemmy.dbzer0.com
      2 hours

      (edit: all of below stuff is only for not being on the same network. After that it gets … messy)

      Oh boy! First: Thank you - I thought to briefly validate my knowledge and understanding before answering and went down a rabbit hole :D this is my current grasp, happy to be corrected!

      First: Most is actually not even distro agnostic but also OS agnostic:

      Most modern wifi devices when you tell them to “connect to WiFi” radiates, literally, what it can do and what kind of connection it wants. E.g. im a wifi device with WPA3 capabilities and this is my Mac address to answer me.

      OS specific is the question if your Mac address gets scrambled or not. For both iwd and networkmanager, which both support it, have it turned off by default. There is a big advantage to being able to be recognizable on friendly networks after all.

      Now comes the part I wasn’t aware:

      Even your hostname is often still broadcasted publicly! This happens during the DHCP handshake - and many devices don’t support apparently existing standards to address this gap. It’s all about securing the first frames where devices align on communication standards, encryption way, etc. This seems to still be quite public.

      Android was easier (and iOS seems to be the same but I didn’t bother with that more): Same as Linux but more aggressive by default: Mac scrambling all the time while searching for networks ,DHCP uses obscure strings as hostnames, etc.

      Fun fact: even those have stable max addresses once connected. Again, getting the same DHCP lease and being able to whitelist or recognized by the network seems to have more upsights than I was aware of.

      • Lytia @lemmy.today
        5 hours

        On iOS and most androids, your Mac address is only scrambled per network. So when you connect to the same network again, your device will use the same Mac address. This generally isn’t an issue if you’re using a private wifi network, or any network where the password isn’t public, but for public wifi it makes it much easier to identify you.

        • Scipitie@lemmy.dbzer0.com
          1 hour

          Thanks for the addition! Edited to make it more clear: there part also referred only to the time before you’ve connected.

        • ms.lane@lemmy.worldEnglish
          3 hours

          And track you, Cisco has had the ability to track MAC addresses over their APs on a map for 2 decades now.

          Also track you over multiple networks- most only care about the SSID- so if you’ve ever connected to “eduroam” you can be tracked across multiple campuses.

          • hard_zero1@discuss.tchncs.de
            2 hours

            Specifically for eduroam, I assume you can be tracked anyways, since you have to authenticate with your personal credentials, right?

    • Maiq@piefed.socialEnglish
      9 hours

      If you and the attacker share the same network the attacker can get all sorts if info.

      Tools like nmap show things like ip, mac, ports and os detection.

      You can use macchanger to randomize your mac. I think there is a setting in networkmanager to do this. Been a while since I looked in the settings.

      • yeehaw@lemmy.ca
        8 hours

        To add to this, I’d be more worried about traffic collection. DNS requests (if your browser isn’t using dnssec then you may not be aware), IPs visited, and other stuff.