virtualbox.org

Hi, I hope this is the right section.

I use virtual box and clones to download junk offers to get credit. I use sandboxy (though I'm not entirely sure how to use it correctly) as well and that definitely helps. It seemed like it was working pretty well, but after about the 15th download, The VM started acting wonky and a few seconds later Norton blocked an intrustion attack attempt on my main PC.

I use Windows 8 as a host actually and Windows 7 home premium 32bit as the VM. I'm wondering exactly the vulnerability of using VMs. How did the attack get outside the VM and target my main PC? I'm assuming through the NAT(is there a difference between NAT and NAT Network?)/ connection which I share with the VM since I'm pretty sure I didn't enable any shared folders.

I'm also worried that since I use public campus internet, if the attack did indeed travel through network to get to my PC, could it affect unknown people using the same wifi?

The Virtual machine is nothing more than a bunch of processes running on your host computer.
So when a antivirus checks the process, it will detect the virus coming in the process of your VM, which is also on your host.
This is especially true since in NAT mode, the Virtualbox processes behave like a regular application trying to access internet files.

There is normally no worries to have for your host, just make sure you have your computer protected the usual way and you should be fine.