It's a female Argiope aurantia. Yes, they belong to the orb weaver family. All spiders are poisonous, that's how their digestive system works. They inject venom into their prey, which liquifies their inner tissues, and then the spider sucks the juices out. The bite of this spider is no worse than a bee sting for a human, but you will never, ever be bitten by any Argiope unless you pick up the spider and hold it against your skin because they never leave their webs. Leave it alone and it will stay there all summer eating insects for you.