When I'm at work, I connect my iPhone to my computer over USB to keep it charged during the day.
When I do so, the phone appears in iTunes. I don't remember my phone prompting me if I wanted to trust my work computer (or I don't remember choosing Yes), but I'd rather not have this connection. All I need is the precious, precious voltage.
Is there any way to remove or un-trust a particular computer?
(My specifics: iPhone 5, iOS 7.0.2, Windows 7, iTunes 11.1)
You cannot untrust with iOS 7. Once you respond with "Trust", you cannot change it. If it's not prompting you now when you connect, it means you have chosen to trust it before.
Snippet from the end of this Apple support article titled "iOS: 'Trust This Computer' alert":
Additional Information
Note: If you select Trust, the computer will be trusted indefinitely. If you select Don't Trust, you will be asked if you want to trust that computer each time you connect your device to that computer.
Last Modified: Sep 18, 2013
With iOS 8, Apple has provided ways to untrust all previously trusted computers (there is no way to untrust computers selectively). Depending on how you do it, this will result in losing your location and privacy settings or losing your network settings or losing everything with the "erase device" option. The 'Trust This Computer' alert on iPhone, iPad, or iPod touch KB article referenced above has been updated as follows:
If you tap Trust, the computer will be trusted until you untrust all computers or you erase the device. If you tap Don't Trust, you'll see this alert each time you connect your device to that computer.
If you're using iOS 8 or later: To untrust all computers, tap Settings > General > Reset > Reset Location & Privacy. This will also reset your location and privacy settings. You can also untrust all computers by tapping Settings > General > Reset > Reset Network Settings. This will also reset your network settings.
Last Modified: Sep 17, 2014
Here is how to do this on a Mac: Go to /var/db/lockdown in Terminal, as Apple instructs in http://support.apple.com/kb/TS5335 . You can remove everything in this folder, which will remove trust from every device -- you can then re-trust those devices you still want to trust. Or you can remove trust for the specific device; this is a little trickier:
First, find out the "Wi-Fi Address" of your device. For an iPhone/iPad, go to Settings->General->About, and scroll down. You'll see a set of numbers and letters that look like "D0:23:DB:6C:B9:13". You'll need this.
Now, on your Mac, fire up Terminal and type:
cd /var/db/lockdown
(Don't forget to press return.) Take that Wi-Fi Address you just found and very carefully search for it like this:
grep -i D0:23:DB:6C:B9:13 *
Instead of my example, use your Wi-Fi Address. You'll see something like this:
39c1082da11b4920c2298dca702ca3795efbf0cc.plist: <string>d0:23:db:6c:b9:13</string>
The long string of numbers and letters ending in .plist (not including the colon) is the file you need to remove! (If you don't see anything, check very carefully that you typed the Wi-Fi Address correctly. If you still don't see anything, then your device likely wasn't trusted in the first place. Be very careful to use zero and not the letter O when you type this string!)
How to remove the file? Well, type:
sudo rm xx...xx.plist
where "xx...xx.plist" is the file that you want to remove ("39c1082da11b4920c2298dca702ca3795efbf0cc.plist" in the example). You can use copy and paste for the file name, or type the first few letters of the name and hit tab. You'll have to type your password (and you need to be set up as an administrator on your Mac), but this will nuke the file and untrust the device with that Wi-Fi address.
(My appologies to the CLI-adept at this long explanation, but even highly adept Mac users don't necessarily grok the Unix command line. And, yeah, I know what a MAC address is, but imagine the confusion!)
grep MACAdress *.plist (might be easier to do even for people not grokking bash)? And welcome to the site!
egrep -i '[0-9a-f]{2}(:[0-9a-f]{2}){5}' *.plist
grep MAC *.plist gives you the name of the plist you want to delete :-)
grep -i "D0:23:DB:6C:B9:13" *.plist. (You'll probably need the -i since, at least in my test, the iPhone used uppercase while the lockdown dir uses lowercase.) I'll edit the original answer to reflect this solution (assuming SE lets me).
Delete the contents inside the Lockdown Folder on your PC leaving the folder itself in place.
This worked for me, both iTunes and all the iOS devices asked me again for authorization the next time they connected.
you may need to pinpoint the correct file if you want to delete only one authorization.
I know this is old but for those who come across it, the above answers especially the chosen one are not completely correct or not specific to the askers setup (Windows 7).
It is possible to "untrust" a computer from the computers side, simply navigate to C:\ProgramData\Apple\Lockdown (start, type in %ProgramData%\Apple\Lockdown )
There there are .plist files that contain the device and host certificates used to pair (trust) and they are named using the iOS devices UDID. Delete the file that pertains to the device you want to unpair (remove trust). Deleting all but SystemConfiguration.plist would work but would also cause all others to have to retrust. You can get the UDID of your device several ways, one of which, since asker said iTunes pops up, is on the main "Summary" page for the device, on top has "Serial Number:" Click once on that and it will toggle to UDID.
The other methods suggested even by apple are not ideal as they also remove the trust from all the devices and also defaults other key settings causing you to have to change them back to how you want them.
This is a serious security issue that I am amazed is not addressed better by Apple. I say serious because it allows bypassing any and all passcodes (current or changed ones in future) needing to be entered in order to have iTunes/Computer access to the device and collect all sorts of data from it. If one has not set a password on encrypt backups (sticks to device not computer) then one could create one and backup the more sensitive data as well. iTunes should have an "untrust" method implemented but they don't. It's literally like a setup where one can sign in (like by using a username password as commonly used instead of entering passcode to unlock and choosing "Trust") and not having a sign out and having the login perpetual, even if you change your password!!
Reset your Privacy settings. This worked for me. Settings > General > Reset > Reset Location & Privacy
Find your WiFi MAC address on the iOS device : Settings > General > About > "Wi-Fi Address"
eg. 40:98:aa:01:02:03
Then on the Mac you wish to remove trust from :
sudo find /var/db/lockdown -name '*.plist' -exec fgrep -i '40:98:aa:01:02:03' {} \; -delete
For Windows and the 'Apple Devices' app released in early 2024: Reset the app to untrust all of the current user's trusted devices on the PC:
Repair options from the Settings page
Select Start > Settings > Apps > Apps & features, or use the URL
ms-settings://appsfeaturesSelect Apple Devices from the list.
Select the Advanced options link under the name of the app. On the page that opens, select Reset.
Note! OP asked about windows process, this is for macOS.
If you remember the date when you “trusted” the device
Settings > General > Reset > Reset All Settings should do this if you really need to un-trust.
Go in Device Manager, find the device and delete the driver for the iPhone. Right Click "Apple Iphone" > Properties > Hardware > Properties > Disable > [OK].
Voila!!!
if you open itunes on the computer that you wish not to trust... there is a bar that has File, Edit, Veiw, Controls, Store, Help
click on "Store" Scroll down and click on "Deauthorize Computer"
