Here are some danger signs the FTC points to:
Your phone battery suddenly starts draining faster.
The abuser has had access to your phone out of your sight. Spyware installation can take from 10 to 25 minutes, depending on the device.
The abuser knows a surprising number of details about your life.
It’s hard to turn your phone off.
Random boots and shutdowns, unusual noise
Strange text messages with different codes or symbols
Higher data USAGE
SOUNDS when your phone is not even being used!
Delay in phone shutting down
You use "pirated" apps
Your phone has been rooted (for Android devices) or jailbroken (for iOS) and you didn’t do it.
The process bypasses software restrictions on the device, and is usually necessary to install spyware
[previously posted in Dec 2016]