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45 lines
2.0 KiB
Markdown
45 lines
2.0 KiB
Markdown
---
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title: "Properly Generate a Randomized MAC Address on macOS"
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date: 2023-08-16
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tags: ['macOS', 'Privacy']
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author: Tommy
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---
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Unlike iOS, macOS does not have an easy way to randomize the MAC address. To work around this, various guides recommended several ways to create a randomized MAC address and apply it to the system during runtime. Unfortunately, most of the instructions do not have a proper threat model in mind and will end up making you stick out more from the crowd.
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### The Threat Model
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Consider the following:
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- macOS does not support MAC address randomization by default
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- Most if not all macOS computers around you will use their real MAC address with Apple's OUI (the first 3 octets of your MAC address)
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- You cannot hide that you are using a mac (because of your hostname, connections to Apple's servers, etc)
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Randomizing the mac address only makes sense if you use a not-very-unique hostname (like Macbook-Pro), and that you only randomize the last 3 octets of your MAC address so that you actually look like a new Macbook on the network.
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### Improper instructions
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Unfortunately, most of the guides I could find recommends randomizing the entire MAC address instead of the final 3 octets. Take the guides recommending `macchanger` for example, they fail to mention that the program does [this](https://github.com/acrogenesis/macchanger/blob/main/bin/macchanger#L37):
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```ruby
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[format('%0.2x', rand(256) & ~1), (1..5).map { format('%0.2x', rand(256)) }].join(':')
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```
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Or this snippet from PrivacyGuides:
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These will give you completely randomized MAC addresses, which is not what we want.
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### Doing it the Proper Way
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First, you need to get the name of your network interface and its MAC address. You can check this with
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```bash
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ifconfig
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```
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In most cases, your interface will be `en0`, the Wifi network interface on modern Macbooks.
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