iOS: Every time you plug your iPhone into a computer, you see the same pop-up on your phone asking if you should "Trust" it. This may seem like a harmless question, but by granting trust to computers, you're essentially giving them access to everything on your iPhone, including photos, videos, contacts and "other content".
Photo: Flickr/Kārlis Dambrāns
That's fine for your own personal computer, but what if you plugged into a friend's laptop so they could download a file? Or charged your iPhone off a public computer at the library and absentmindedly clicked "Trust" on the pop-up? In that case, you'll want to "un-trust" those computers so your private data stays secure. Unfortunately, Apple doesn't exactly make it easy to do this, but there are a few different ways you can pull it off (via GadgetHacks) without too much extra work.
The easiest option is to reset your Network Settings. The only catch is that it removes all the Wi-Fi passwords saved to your phone too. That might be a little annoying, but it will also clear out any old Wi-Fi networks that you no longer use. To do it, open the Settings app, go to General, and select Reset. Then tap on "Reset Network Settings" and enter your password to confirm.
If you'd rather not lose your Wi-Fi passwords, you can also un-trust computers by resetting Location & Privacy settings on your phone instead. Head to the same page (Settings > General > Reset), select "Reset Location & Privacy", and confirm with your passcode. This will also revoke all permissions granted to other apps (things such as access to your iPhone's camera, microphone, location and saved photos). So if you do it, a lot of other apps won't work until you give back the permissions they need.
Your third and final option is a total factory reset, which will remove everything on your iPhone. We don't really recommend this unless you're planning on giving away the device, but if you want to do it just head to the same Reset page and select "Erase All Content and Settings".
Whichever option you choose, you'll be losing a little functionality (at least temporarily) in exchange for some extra iPhone security. Just think of it like spring cleaning for your smartphone, and un-trust your device at least once a year to stay safe.