Agressive Jack Russel

Question
I have a three year old female JR.  She is very lovable except she attacks anyone that comes on my property or goes by.  She has bit three people this week.  She is also agressive towards my male JR when she is around the family.  I don't know what to do.

Answer
Take her to a professional behaviorist and/or trainer
People don't really want to hear it or admit it but most aggression problems stem from the OWNERS.
No offense is intended at all - it's just the way it is..
People don't even realize they are doing anything wrong, but they have to be very confident in teaching their dog how to deal with stress and aggression.
You are probably not showing pack leadership and might be  correcting her in the wrong way. People use too many human words and corrections and get all emotional which the dog interprets as stressful.
Aggression and allergies are the result of stress, panic, or other uncomfortable reactions in the living environment and is a way of self preservation on the part of the dog.
I would suggest Cesar Milan's tapes and books and a professional dog trainer to help you
Good luck.