Privacy

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Privacy concerns with DHCP (DHCP fingerprinting) (lemmy.zip)

submitted 4 months ago* (last edited 4 months ago) by [email protected] to c/[email protected]

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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

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[–] hostops 6 points 4 months ago (4 children)

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

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

Do not connect to public networks
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.

[–] [email protected] 3 points 4 months ago (1 children)

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.

[–] hostops 0 points 4 months ago

But the reasoning stays the same.

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