Prevent a specific USB device from auto-mounting

Using the terminal and gedit

First find the ID for your device from a terminal using lsusb when your device is connected (eg 0951:1692). Also you should to find what is the name of your device with lsblk. Let say the name is /dev/sdb1.

Create a new script, let say unmount.sh in /lib/udev with sudo -H gedit /lib/udev/unmount.sh and put next lines inside:

#!/bin/bash

udisks --unmount /dev/sdb1
udisks --detach /dev/sdb

Save the file, close it and make it executable with:

chmod +x /lib/udev/unmount.sh

Now, you must to make a new rule file in /etc/udev/rules.d/ with sudo -H gedit /etc/udev/rules.d/100-unmount-iphone.rulesand put a new rule in there like this:

ACTION=="add", ATTRS{idVendor}=="0951", ATTRS{idProduct}=="1692", RUN+="/lib/udev/unmount.sh"

To reload udev rules without restart, use next command:

sudo udevadm control --reload-rules

Using Cuttlefish

Or, another way is to install and use Cuttlefish - a simple tool that realises reflexes on your computer.