If they actually enter an unlocked car, at best it's trespassing. If they cause damage or theft, now that is illegal. With a computer it is much harder to prove damage and theft and trespassing is a misdemeaner DO NOT call our tech support to report that you have been scanned, there is very little we can do. You can find the ISP they belong to and send them a copy of your logs asking that they look into it. If they get enough compaints, and they can track it to the same individual, they will probably cancel their account.
Prevention IS the best medicine.