How do I scan for viruses on my iPhone?

There is no way for anything to scan your device. That is a good thing, because that also means that nothing has access to your file system to install any viruses.

There is not a way for a file to be downloaded and not visible to you. Only you can hide files and those are available to you in the Hidden Folder of your App Library.

You always have the option to run Safety Check on your device that will let you review information that you are currently sharing to others along with the ability to change your password/passcode.

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

AuthKitUIService is essentially an app that allows third-party applications to use authentication methods such as Touch ID and Face ID. 

Newnow25 wrote:

Thanks! Maybe a stupid question

No such a thing as a stupid question 🙏

but it wouldn’t be easy for someone to remotely control my phone right?

That is correct. It would require a ton of expertise and a whole pile of money. Something like $100K. Not even the FBI can hack iPhones.

Or at least I’d notice something?

Probably you would.

Again I’m very paranoid, I know!

Aren’t we all.

Newnow25 wrote:

Last question - do you by any chance know what Authkit ui service and user authentication are used for?

I’m sorry I do not. But hopefully someone will respond who does know. Perhaps you could post a screenshot so we can see what you are seeing? Make sure to black out personal information.