How to know if my iPhone might be hacked or not?

Review if there are any other devices signed into your account at Settings > [name on top], and scroll to the bottom to view the devices. For any that are not yours, tap on them to remove and follow up by changing your Password.

Change your Apple Account Password:

Change your Apple Account password - Apple Support

To prevent physical access to your device, change the Passcode:

Set a passcode on iPhone - Apple Support

If you were a victim of a phishing attempt where someone convinced you to give them your password by claiming they were a legitimate source, review the information provided here and never call a number or click a link in an email/message and provide any personal information.

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

Without any further information, such as Social Media usage where you have allowed them to access your Photos, review the information provided here:

Personal Safety User Guide - Apple Support

It's highly unlikely you've been hacked unless your phone is jailbroken. It's HUGELY difficult and HUGELY expensive to hack an iPhone.

Possible things which could be a factor:

1. Photos in WhatsApp or some other social media platform which automatically downloaded to your phone if you haven't turned off that feature in the app(s).
2. Perhaps you share an Apple Account (formerly referred to as Apple ID) with another person?
3. Read this link if you think your phone could have been compromised --> If you think your Apple Account has been compromised - Apple Support

That sounds concerning. First, check if your iCloud account has been accessed from another device by going to Settings > [your name] > Devices. Change your password right away and enable two-factor authentication. Also, scan for any suspicious apps or profiles. If things still seem off, consider backing up important data—like photos or travel plans such as desert safari dubai tickets, and resetting your phone to stay safe.

[Edited by Moderator]

It is common for scammers to claim that your iPhone has "viruses", that it has been "hacked", or that hackers are "watching your every move" and about to "leak your information to the dark Web." A few of the scam messages even claim that your device will be "permanently damaged" if you do not act right now.

All lies, sent by criminals who are hoping to scare you (and other potential victims) so badly that you will deliver yourself into their hands to be ripped off.