Dogs are able to identify people with bad intentions towards them or their owners

from their behavior as pack animals.
Postures and behaviors: how do you know what your dog is feeling?

Dogs communicate with the body. Knowing how to read their postures can help you interpret if they are comfortable, nervous, or feel that something is not right:

Ears back and tense body: a clear sign of alert or discomfort.
Growling or barking directed at a specific person: form of warning or defense.
To interpose between the owner and someone else: protective attitude, possibly because of perceiving danger.
Eyes wide open, dilated pupils: indicates nervousness or fear.
Avoid approaching or hide: if they