Sudden battery drain
Phone overheating when not in use
Unexpected pop-ups or ads
Apps crashing or freezing
New apps you did not install
Unusual data usage spikes
Slow performance
Phone behaving strangely on its own
Unknown charges or messages sent
Browser redirects to strange websites
Security settings changed without your permission
Antivirus or system warnings appearing repeatedly
Calls, texts, or contacts you do not recognize
Device restarting unexpectedly
Apps requesting unusual permissions