Hackers who exchange pirated software are always looking for places to make their software available for download to their friends and co-pirates. My new 18 gigabyte hard disk may be just what they have been looking for. OK, I'm convinced that it's a bad thing to just leave my computer connected to the Internet all the time. But I like the convenience of being able to access the Web on a second's notice. For the most part, changing a few settings, installing a personal firewall, maintaining updated antivirus software, and a little common sense will provide me with reasonable protection at a very resonable cost.
Every computer connected to the Internet has a unique address.
Without this address, it would be impossible for the computer to work. It's like every telephone having a unique phone number. You don't have to know the number to make a call, but without it, the phone won't work. Hackers are just like tele-marketers. They start with a known number, and keep adding one to it and trying this new number.