If you are concerned about malware on an iPhone, focus on verifiable security problems instead of expecting a desktop-style antivirus scan. Battery drain, heat, crashes, pop-ups, or slow performance can have ordinary causes and do not prove that iOS is infected.
Install current iOS security updates
Open Settings > General > Software Update and install the newest update available for the iPhone. Security fixes are distributed through software updates, making this one of the most important routine protections.
Review apps you do not recognize
Look through installed apps and investigate anything unfamiliar. Remove an app you no longer trust after determining what it is. Work, school, banking, and device-management software can have unfamiliar names, so identification is better than deleting blindly.
Inspect VPN and device-management profiles
Open Settings > General > VPN & Device Management. An unexplained configuration or management profile on a personal iPhone deserves investigation. Employer- or school-managed phones can legitimately contain profiles, so consult the administrator before removing one that may be required.
Check the Apple Account
Open Settings and tap your name, then review associated devices and security information. Unexpected verification codes, password changes, purchases, sign-in alerts, or unfamiliar devices can be stronger indicators of account compromise than vague performance symptoms.
Understand the limits of iPhone antivirus apps
iOS isolates apps and restricts their access to the operating system and to other apps. An ordinary consumer security app therefore cannot perform an unrestricted forensic scan of the entire iOS system. Such apps can still provide features such as malicious-site warnings, account monitoring, or network tools, but a clean result is not a forensic guarantee that every part of the phone was inspected.
Ignore fake malware scans in web pages
A webpage claiming that it scanned your iPhone and found several viruses is not reliable evidence of infection. Do not install an unknown profile, download a cleaner, call a displayed number, or enter Apple Account credentials because a pop-up tells you to.
Take genuine Apple threat notifications seriously
Apple can warn users it believes may have been individually targeted by sophisticated mercenary spyware. That situation is different from a generic browser warning. Verify a suspected notification through your Apple Account and follow Apple’s current guidance, including qualified security assistance when appropriate.
Do not erase the phone based on symptoms alone
A factory reset can be disruptive and should not be the automatic response to ordinary battery or performance problems. Update the phone, secure accounts, investigate apps and profiles, and determine whether there is credible evidence of compromise first. In a serious targeted case, preserving evidence before destructive changes can be important.
Matthew Roberts created this site to help his friends and family with questions that they might have about how to change the settings on their iPhones. It now serves as an archive of iPhone how-to guides to help anyone that stumbles upon this website.