Strangers - If the person reminds you of someone you know.. think about your relationship with him or her, and the issues that the dream has brought up, or how you relate to the person that is being represented. If these people are totally unrecognizable (they don't remind you of anyone you know)... they would represent different, and unknown, aspects of yourself. They are extensions and projections of your own subconscious, and personality. Alternately, a stranger may represent an unknown fear, or danger, you feel in your waking life.

Intruders would suggest you feel as though someone is intruding into your private space in your waking life.
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Is there anyone new in your life somewhere and they're trying to ingratiate themselves to you? (new neighbors, coworker, boss, etc.)

Hope I could give you some insight. Good luck!