I'm new to working with and using a backdoor/virus with a boot disk.
- Can they be mounted to a USB drive?
- What options are out there and what should I look for in one?
- Are they practical?
- Do they need to be upgraded/replaced every few months?
Check out YUMI and XBoot at: http://www.pendrivelinux.com/tag/multiboot-live-usb/
These will let you boot many CD/DVD ISOs from a USB stick. Not every ISO works, but pretty much anything that is Linux based (as most bootable antivirus disks are) will work, and some PE based disks will work as well.