Samsung does not recommend that you root your phone in any way. Rooting your phone would void your warranty. We only recommend that you download apps from the play store.
Only phones on contract have locked bootloader, plus there is always a way. Might be hard to find or hard to do but there is a way. Plus you shouldn't need to root your phone anyways I do alot of app disabling and installing apk without rooting my device.
The phone being compromised how? Depending on how they get in that could be really bad. Are they getting in to your google account because all your accounts and password are saved on google.