How to spoof MAC address and hostname automatically at boot on macOS

Heads-up: unfortunately, it is not possible to spoof MAC address on some Macs (see issue).

Requirements

• Computer running macOS Catalina or Big Sur

Caveats

• When copy/pasting commands that start with $, strip out $ as this character is not part of the command
• When copy/pasting commands that start with cat << "EOF", select all lines at once (from cat << "EOF" to EOF inclusively) as they are part of the same (single) command

Guide

Step 1: create /usr/local/sbin directory

sudo mkdir -p /usr/local/sbin
sudo chown ${USER}:admin /usr/local/sbin

Step 2: add /usr/local/sbin directory to PATH environment variable

echo 'export PATH=$PATH:/usr/local/sbin' >> ~/.zshrc
source ~/.zshrc

Step 3: download first-names.txt

This list includes top 2048 most popular names for people aged 25 from the USA Social Security Administration (last updated on March 9th 2022).

curl --fail --output /usr/local/sbin/first-names.txt https://sunknudsen.com/static/media/privacy-guides/how-to-spoof-mac-address-and-hostname-automatically-at-boot-on-macos/first-names.txt

Step 4: create spoof.sh script

cat << "EOF" > /usr/local/sbin/spoof.sh
#! /bin/sh

set -e
set -o pipefail

export LC_CTYPE=C

basedir=$(dirname "$0")

# Spoof computer name
first_name=$(sed "$(jot -r 1 1 2048)q;d" $basedir/first-names.txt | sed -e 's/[^a-zA-Z]//g')
model_name=$(system_profiler SPHardwareDataType | awk '/Model Name/ {$1=$2=""; print $0}' | sed -e 's/^[ ]*//')
computer_name="$first_name’s $model_name"
host_name=$(echo $computer_name | sed -e 's/’//g' | sed -e 's/ /-/g')
sudo scutil --set ComputerName "$computer_name"
sudo scutil --set LocalHostName "$host_name"
sudo scutil --set HostName "$host_name"
printf "%s\n" "Spoofed hostname to $host_name"

# Spoof MAC address of Wi-Fi interface
mac_address_prefix=$(networksetup -listallhardwareports | awk -v RS= '/en0/{print $NF}' | head -c 8)
mac_address_suffix=$(openssl rand -hex 3 | sed 's/\(..\)/\1:/g; s/.$//')
mac_address=$(echo "$mac_address_prefix:$mac_address_suffix" | awk '{print tolower($0)}')
networksetup -setairportpower en0 on
sudo /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport --disassociate
sudo ifconfig en0 ether "$mac_address"
printf "%s\n" "Spoofed MAC address of en0 interface to $mac_address"
EOF

Step 5: make spoof.sh executable

chmod +x /usr/local/sbin/spoof.sh

Step 6: create local.spoof.plist launch daemon

cat << "EOF" | sudo tee /Library/LaunchDaemons/local.spoof.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>local.spoof</string>

    <key>ProgramArguments</key>
    <array>
        <string>/usr/local/sbin/spoof.sh</string>
    </array>

    <key>RunAtLoad</key>
    <true/>
  </dict>
</plist>
EOF

Step 7: create spoof-hook.sh script

cat << "EOF" > /usr/local/sbin/spoof-hook.sh
#! /bin/sh

# Turn off Wi-Fi interface
networksetup -setairportpower en0 off
EOF

Step 8: make spoof-hook.sh executable

chmod +x /usr/local/sbin/spoof-hook.sh

Step 9: make sure com.apple.loginwindow does not exist

Heads-up: if com.apple.loginwindow exists, one needs to backup user default carefully and consider using an abstraction that runs both current LogoutHook script and /usr/local/sbin/spoof-hook.sh.

$ sudo defaults read com.apple.loginwindow
2021-09-27 06:58:02.301 defaults[2267:25227]
Domain com.apple.loginwindow does not exist

Domain com.apple.loginwindow does not exist

👍

Step 10: configure user default (used to disable Wi-Fi interface at logout)

sudo defaults write com.apple.loginwindow LogoutHook "/usr/local/sbin/spoof-hook.sh"

Step 11: reboot and confirm hostname and MAC address have been spoofed

Spoofed hostname

$ scutil --get HostName
Ottos-MacBook-Pro

Spoofed MAC address

$ ifconfig en0 | grep ether | awk '{print $2}'
98:01:a7:8e:0f:51

Hardware MAC address

$ networksetup -listallhardwareports | awk -v RS= '/en0/{print $NF}'
98:01:a7:5e:d0:c2

“Spoofed hostname” is random and “Spoofed MAC address” does not match “Hardware MAC address”?

👍

Want things back the way they were before following this guide? No problem!

Step 1: delete files

rm /usr/local/sbin/first-names.txt
rm /usr/local/sbin/spoof-hook.sh
rm /usr/local/sbin/spoof.sh
sudo rm /Library/LaunchDaemons/local.spoof.plist

Step 2: delete user default

sudo defaults delete com.apple.loginwindow LogoutHook

Step 3: set computer name, local hostname and hostname

Heads-up: replace John with your name.

sudo scutil --set ComputerName "John’s MacBook Pro"
sudo scutil --set LocalHostName "Johns-MacBook-Pro"
sudo scutil --set HostName "Johns-MacBook-Pro"

Step 4: reboot

👍