There are a lot of apps on the app market that allege to help and protect your iPhone, but I've yet to hear of a good antivirus for MAC (let alone iPhone). For PC there's a bunch like kapersky, mobile antivirus is still so new.
As an Apple Device owner, and a previous apple worker, I can tell you that apple devices DO NOT get viruses or get infected. There may be so called antivirus programs on the app store, but they are a scam. Apple Devices, things like, iPods, iPhones, and iPads can't get viruses because of the system they run on, and how they are on limited on features.
What about mp3s and jailbroken phones? I mean as long as a user can import files and content on the device, there will always be a chance they can install malware isn't there?
Also, the theory that MACs can't get a virus is wrong - in the past, people believed this - but it's really a matter of ROI. Viruses are made for profit - since mac users were a small minority, it didn't make sense to invest money and time into making a virus that could only net you profit if installed on a mac machine. But now that the popularity of those devices has increased, it makes more fiscal sense to create malware for macs.
TL;DR: Wherever there's popularity, fraudsters will find a way to exploit it. iOS usage is growing and malware creators will soon create viruses for it.
I think Apple just does "anti virus" differently. I'm not an Apple user, but my guess would be that there would be a tab somewhere for checking for updates or upgrades from the Apple download site. Probably good to read reviews about the updates first before installing them, just come across this one that didn't seem to go that well:
iPhone doesn't need an Anti-virus if not jail-broken but need only legit apps installation if you add any other 3rd party soft there where the risk grow, I guess this essentially what's apple Sandbox was designed
Since it is limited to install from Apple, antivirus software is unnecessary. However, if you are concerned about malware other than virus, unknown virus, you can purchase it, but you need to connect to the Internet.
In order to prove that the delivery is not infected with the virus, there are cases to purchase. Of course, in order to update the definition file, you need to connect to the Internet.