The most serious vulnerability on your iPhone isn't your iPhone itself, but the passwords used on your iPhone to access your data. If you use the same password on multiple websites or services, then you're at risk. Hackers target websites and services that don't seem like they would hold valuable information, like a forum that requires a login. When the hackers get in there, they harvest large lists of passwords. The hackers know that some of those same credentials will have been used in other, more important services, like iCloud. They try on iCloud with all the usernames and passwords they got from the low-security service, and every now and then, they get lucky.
Hackers usually aren't after you personally, so anonymity isn't a good defense. They may not even know your name. If they manage to penetrate a website that has a password of yours, and you used that same password with iCloud or your Apple ID, then they may get onto your iCloud account. They might place files on your iPhone with iCloud, see your photo stream, send emails using your accounts, or mine your personal data from your iCloud backups.
Fortunately, Apple has an easy-to-use solution in iCloud Keychain. This service generates secure passwords and stores them, so you don't have to remember, and so every password is unique
If you use iCloud Keychain, you don’t have to worry about remembering your passwords, or about duplicate passwords. But there is a downside: anyone who gets into your iCloud account will have access to all your passwords! You’ve got to make your Apple ID (or iCloud ID if you haven’t combined them) really, truly, secure. Use Two-Factor Authentication, Apple’s latest failsafe.
When Two-Factor Authentication is enabled, you have to use a trusted device to log in to a new device. For example, say you got a new iPad. When you go to sign in with your Apple ID for the first time, your other trusted devices like your iPhone will receive a notification asking for approval. If allowed, your iPhone will display a verification code. Once you enter the verification code on your iPad, the device is approved. This feature works so well because anytime someone tries to log in to your Apple ID account, you’ll get a notification and have the ability to approve or deny the attempt. This feature requires iOS 9 or later and has been the default since iOS 11. To turn on Two-Factor Authentication:
A lot of iPhone users may be skeptical of this advice, and for good reason. Updating your iOS devices to the latest software is the absolute best way to make sure your devices are as protected from hackers as possible. That’s because with each update, Apple improves security features and fixes any previously overlooked weak points that might allow hackers access. But the first couple of weeks after an iOS release often reveal problems with the update itself. This is why I highly recommend you update iOS regularly on your phone, but not right away. A week or two is enough time for any major flaws or bugs to become apparent. When a new update comes out, wait two weeks and then go for it. To update your device: This is a no-brainer. When Find My is turned on for your iPhone, you can see the location of your iPhone from any of your other devices or any computer via iCloud.com.
While it’s not recommended you personally track down an iPhone that’s fallen into the hands of a thief, Find My iPhone will allow you to find your device if you lose it. However, that’s not why it’s recommended for protecting your device from hackers. The great thing about Find My iPhone is that if your device is stolen, you can remotely erase your device so that none of your personal information can be stolen too.