Sudden battery drain
Phone overheating when idle
Unusual data usage spikes
Random pop-ups or ads
Apps you did not install
Apps crashing or opening by themselves
Slow performance or frequent freezing
Unknown calls, texts, or emails sent from your phone
Strange activity on your accounts
Settings changed without your permission
Microphone, camera, or location turning on unexpectedly
Unfamiliar login alerts
Phone restarts on its own
High background activity
Passwords no longer working
Security warnings from your carrier or accounts