TL;DR: Signs an app may be spyware include requesting permissions that have nothing to do with its stated purpose (a calculator app asking for microphone or contacts access), unusually high background data or battery use, and being hidden from the home screen or disguised under a generic name/icon. Review app permissions under Settings > Privacy & Security (iPhone) or Settings > Apps > Permission manager (Android), uninstall anything suspicious or unrecognized, and run a reputable security scan on Android since iPhone doesn't allow direct scanning of installed apps.
Signs an app may be spyware include requesting permissions that have nothing to do with its stated purpose (a calculator app asking for microphone or contacts access), unusually high background data or battery use, and being hidden from the home screen or disguised under a generic name/icon.
What Usually Causes This
Spyware apps are often installed deliberately by someone with access to the device, disguised as a utility app, or occasionally bundled with software downloaded from outside the official app store.
What to Do About It
Review app permissions under Settings > Privacy & Security (iPhone) or Settings > Apps > Permission manager (Android), uninstall anything suspicious or unrecognized, and run a reputable security scan on Android since iPhone doesn't allow direct scanning of installed apps.
If this looks similar to something else you've seen, it's worth reading How to Tell If Someone Is Reading Your Texts.
This pattern shows up elsewhere too — see How to Tell If Someone Cloned Your SIM Card.
Frequently Asked Questions
What are the real warning signs?
Signs an app may be spyware include requesting permissions that have nothing to do with its stated purpose (a calculator app asking for microphone or contacts access), unusually high background data or battery use, and being hidden from the home screen or disguised under a generic name/icon.
What usually causes this?
Spyware apps are often installed deliberately by someone with access to the device, disguised as a utility app, or occasionally bundled with software downloaded from outside the official app store.
What should I do about it?
Review app permissions under Settings > Privacy & Security (iPhone) or Settings > Apps > Permission manager (Android), uninstall anything suspicious or unrecognized, and run a reputable security scan on Android since iPhone doesn't allow direct scanning of installed apps.
Should I be worried if I only see one sign?
One sign alone (like a slower device) is usually not cause for alarm — most single symptoms have mundane explanations. Multiple signs together, especially unexpected data usage or unfamiliar apps, are worth investigating.