iPhone security and no viruses

I don't know that it's "not possible" but the following has information that may be helpful: Apple Platform Security - Apple Support

Hi this might help.

Apple designed the iOS so that every app runs in its own, restricted "space." While iOSapps can communicate with each other, those options are limited. By restricting the ways apps interact with each other and with the operating system itself, Apple reduced the risk of viruses on the iPhone

Because it's a locked down OS. Even apps you purchase via the App Store cannot touch another app. This makes any AV software you see in the App Store totally useless. The only thing it can check for malware is itself.

Most aren't AV software at all, but charge you to do simple things you can do yourself without it. Like clearing Safari's cache data. The closest them come to acting like AV software is they may look at your email and tell you if something has a suspicious attachment.

iOS uses a “sandbox” model. No app can access the operating system itself, and each app can only access data that it created or imported into its work area or “sandbox”. Further, it is not possible for anyone, even the owner, to access content without using the app that owns that content. For a techie answer, that means that the “root” password is not determinable, and there is no “su” or “sudo” command that can give an ordinary user privileged access.

However, there are still bugs that might allow a user to bypass the secure model. So Apple deals with those by quickly release updates to block them. iOS 13.5.1 was one such update that fixed an obscure vulnerability that was discovered by a security researcher. Apple pays well for such discoveries and reports; one such recent payment was $100K.

You should have 12.7.4. That is the current secured version.

Anything can be hacked in theory. But cybersecurity is not a “wall”, it is an arms race. For every vulnerability there must be an immediate response, and Apple is very good about keeping up.

12.4.7 is the version that has blocked all known vulnerabilities. If an additional vulnerability is discovered Apple will issue an update to block it. These things are very rare, so your phone will be secure.

BTW, you used “virus” generically. No iPhone has ever had a virus, using the narrow definition of “virus” which means a vulnerability that can spread from one device to another, the way human viruses do. There are many types of “malware” that are not viruses (although all viruses fall into the malware category) that can cause damage to one device if installed on it. There is currently no known malware (in the broadest category) that can get into an iPhone that isn’t jailbroken.

Impossible or not possible is an extremely high bar. As Lawrence (highly respected) noted in his reply "However, there are still bugs that might allow a user to bypass the secure model."