How can I detect and block unauthorized access to my iPhone?

If you feel an unauthorized person/app is remotely using, controlling or monitoring your device, then that is possible only if you have done one or more of the following Don'ts...

1. Don't hand over an iPhone to kids or to a stranger without Enabling Guided Access
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device
5. Don't give in to Phishing
6. Don't plug in your device in Airports and Public places through third-party cables and trust the device. Beware of Juice Jacking. (Especially in India)
7. Don't leave your iPhone unlocked and unattended in public places like offices, schools, malls, etc.

If one of the above is true then quickly change the Apple ID Password and Return iPhone settings to their defaults.

Rigoslastbreath wrote:

there’s plenty of YouTube videos that clearly show there are simple ways to get into your phone without even touching it so I done nothing wrong and you obviously do not have all of your information of what can and can’t be done by mirroring checking somebody’s phone and getting into it so I find her information not useful

There are also YouTube videos claiming the world is flat. They mean nothing. The only thing they are looking for is to get upvotes and increase views to line their pockets.

Change your Passcode and Password on your account. Perform Safety Check to also see if someone else is logged into your account and to review data to be shared.

Safety Check for an iPhone with iOS 16 or later - Apple Support