Unrecognized Calls: Calls from unrecognized numbers could indicate you’ve been the victim of a data breach
Pop-ups: If you’re seeing a lot of pop-up ads, your phone could have an adware infection
High Data Usage: A malicious app running in the background can cause unusually high data usage
High Battery Drain: Unwanted apps on your phone can hijack your phone’s resources and drain your battery
Hot Phone: Malicious software might be causing it to overheat, even if your are not using phone much
Unexpected charges on your phone bill: Fleeceware apps stuff your bill with excess charge
Apps you don’t install but is still on phone: Strange apps that you didn't install shouldn’t end up on your phone
Changes to settings: Sign your phone is hacked is if you notice new and unfamiliar changes to the settings of your device
Websites look strange: Phone infected with malware can redirect you to unwanted, infected websites