So many people here will go though great lengths to protect themselves from fingerprinting and snooping. However, one thing tends to get overlooked is DHCP and other layer 3 holes. When your device requests an IP it sends over a significant amount of data. DHCP fingerprinting is very similar to browser fingerprinting but unlike the browser there does not seem to be a lot of resources to defend against it. You would need to make changes to the underlying OS components to spoof it.

What are everyone’s thoughts on this? Did we miss the obvious?

https://www.arubanetworks.com/vrd/AOSDHCPFPAppNote/wwhelp/wwhimpl/common/html/wwhelp.htm#href=Chap2.html&single=true

  • irq0@infosec.pub
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    4 months ago

    I feel like I’m missing something here…

    Who’s going to be fingerprinting DHCP messages on your home network?

    Outside of that, fingerprinting or tracking any DHCP info would be the least of my concerns. You have 0 control over any data the moment your devices connect to a public network. What use is DHCP info when you can person-in-the middle all the traffic anyway?

    And anyway, what info are you concerned about? Having had a VERY quick browse of RFC2131 the worst thing would be “leaking” the device MAC address which can be discovered via several other means anyway

    • Max-P@lemmy.max-p.me
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      4 months ago

      I guess the hostname could be used to defeat MAC randomization if you use public WiFi like hotels, airports and coffee shops. You could probably identify repeat users if you cared enough.

      But then your worry should be the security cameras not the WiFi, because that’s what’s gonna tie you personally to your device connecting.

      • 14th_cylon@lemm.ee
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        4 months ago

        Your router always knows your Mac address, no matter how you got your ip assigned. And yes, you can use it to identify the client - that is why it is there. This whole post is nonsense written by someone who doesn’t really understand what dhcp is or how it works. Long story short, don’t look for privacy on local Ethernet segment :D

        • Max-P@lemmy.max-p.me
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          4 months ago

          Most modern operating systems randomize the MAC. DHCP does have extra fields such as the device’s hostname that can be used to counter that.

          But as I said, that’s unlikely to be the weakest link. If you don’t trust the network you’re also likely in a public environment where people can just see you anyway.

          • user134450@feddit.org
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            4 months ago

            Most modern operating systems randomize the MAC.

            [citation needed]
            having the option to randomize the MAC is not the same as actually doing that. There are also a few downsides to random MACs, like captive portals not remembering you on public WiFis.

          • 14th_cylon@lemm.ee
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            4 months ago

            Most modern operating systems randomize the MAC.

            that doesn’t seem to be uniform behaviour. but i think we agree on the merit. if you are this paranoid, you just don’t use networks where you don’t have control over the local segment.

            [admin@MikroTik] > ip arp print 
            Flags: X - disabled, I - invalid, H - DHCP, D - dynamic, P - published, C - complete 
             #    ADDRESS         MAC-ADDRESS       INTERFACE                                                    
             0 DC 192.168.88.160  A2:35:xx:xx:xx:xx bridge                                                       
             1 DC 192.168.88.159  F4:60:xx:xx:xx:xx bridge                                                       
             2 DC 192.168.0.1     44:32:xx:xx:xx:xx ether1                                                       
             3 DC 192.168.88.168  18:3D:xx:xx:xx:xx bridge                                                       
             4 DC 192.168.88.156  70:BB:xx:xx:xx:xx bridge 
            

            • ReversalHatchery@beehaw.org
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              4 months ago

              you just don’t use networks where you don’t have control over the local segment.

              Easier said than done. Sometimes it’s not an option.

              • 14th_cylon@lemm.ee
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                4 months ago

                there is always an option. unless you are pressured by lets say some state authority or your employee, in which case your identity is probably well known and they don’t really need to spy on you through dhcp.

        • ReversalHatchery@beehaw.org
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          4 months ago

          Long story short, don’t look for privacy on local Ethernet segment :D

          You seem to be forgetting that a lot of people use portable devices on other networks than their home one.

          • 14th_cylon@lemm.ee
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            4 months ago

            i am not forgetting anything. using your portable device on network other than your own is your free choice and if you are such control freak that you are afraid of being spied on through dhcp, you probably should not do that.

        • Bitrot@lemmy.sdf.org
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          4 months ago

          You need to say more than that about what your concern is, especially on devices configured for Mac randomization and other privacy features.

          Aruba is looking at the dhcp traffic and inferring information about the device. The device is not sending all of this data.

    • Possibly linux@lemmy.zipOP
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      4 months ago

      Hostname, platform, OS version, software versions and other data are all sent.

      Most commercial wireless networking software can fingerprint a device with a decent certainly

      See the link

      • s38b35M5@lemmy.world
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        4 months ago

        I used to provide commercial end-user support for a network intelligence product that used as much metadata as possible to help classify endpoints, shuffling them off to the right captive portals for the right segment based on that data.

        I can tell you that the things you’re saying are transmitted in a DHCP request/offer are just not. If they were, my job would’ve been a LOT easier. The only information you can count on are a MAC address.

        I can’t view that link you shared, but I’ve viewed my share of packet captures diagnosing misidentified endpoints. Not only does a DHCP request/offer not include other metadata, it can’t. There’s no place for OS metrics. Clients just ask for any address, or ask to renew one they think they can use. That only requires a MAC and an IP address.

        I suppose DHCP option flags could maybe lead to some kind of data gathering, but that’s usually sent by the server,not the client.

        I think, at the end of the day, fighting so that random actors can’t find out who manufactured my WiFi radio just isn’t up there on my list of “worth its” to worry about.

  • hostops@sh.itjust.works
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    4 months ago

    DHCP only acts in local networks which is in 90%:

    1. home network where you trust every device to not spy on you
    2. office network where in most cases your emloyer provided you with the hardware. And in 10%:
    3. Public WiFi

    The only thing leaked in DHCP is your MAC. Attacker can use this info to identify brand of our network adapter. Or if they have really huge database of laptop manufacturers attacker can identify your device. If you use VPN or TOR the only thing they know from now on is that you use VPN or TOR. And if they really have everything in that database they will be able to tell who bought that computer. So now attacker can only knows who is in their netwotk.

    Which is useless in scenario 1. and 2. Where you already know who is in your network and owner of that network has no database to identify you based on your MAC.

    In scenario 3. If we are talking about huge public networks like WiFi provided from your town. If infiltrated by 3 letter agencies which may have such database they could theoretically track your location based on which town network you connected to.

    But you can protect yourself from this:

    1. Do not connect to public networks
    2. Your OS/Network card driver allow you to use random MAC address. Just enable random MAC in your network settings. In Android: WiFi > Select specific network > Privacy > Use randomized MAC.

    Also take note some general location tracking can already be done through mobile networks.

    • refalo@programming.dev
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      4 months ago

      The only thing leaked in DHCP is your MAC

      This is not true. It also leaks your hostname by default and often your previously associated IP. There’s also vendor-specific “DHCP option” sets that can hold extra data too, which some OSes might use to leak additional info.

    • Schwim Dandy@lemm.ee
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      4 months ago

      Does randomizing your MAC create any usability issues? Needing to log in repeatedly, getting bumped off network due to looking like a different device, anything else hindering usability?

      • makeasnek@lemmy.ml
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        4 months ago

        No, you may have to re-login every time you connect, but once you connect, your MAC would be stable for that session.

  • TCB13@lemmy.world
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    4 months ago

    When your device requests an IP it sends over a significant amount of data.

    Like…?

  • jet@hackertalks.com
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    4 months ago

    Using randomized MAC on my phone’s, and observing the behavior on my network. It works fine, the router can’t assign a ip to the device because the physical address changes. The os fingerprinting still works, the gateway knows what kind of device it’s talking to.

  • MonkderDritte@feddit.de
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    4 months ago

    I mean, yeah. Lots of shopping centers have devices specialized on fingerprinting mac adress. It was already 10 years ago a thema that you should disable wlan and bluetooth if you go out of the house.