Check for unusual battery drain
Check for unexpected data usage
Look for unfamiliar apps
Review app permissions
Watch for random pop-ups or ads
Check for overheating when idle
Notice slow performance or crashes
Look for strange texts or calls sent from your phone
Check if settings change by themselves
Review login alerts on your accounts
Look for unknown devices signed into your accounts
Check if your phone restarts unexpectedly
Watch for microphone or camera activity indicators
Scan for malware with a trusted security app
Check for forwarding rules on calls, texts, and email
Verify whether your phone is rooted or jailbroken
Review installed profiles or device administrators
Check for unknown VPNs or proxy settings
See if your contacts receive strange messages from you
Monitor for apps opening on their own
Back up important data and reset the phone if needed