If you have a computer which is not connected to Internet (or other networks, LAN, Wireless network...) you can call it a standalone computer.
Of course viruses can be spread through floppy disks, usb keys or other methods so being a standalone computer not connected to any network doesn't mean the computer can not be infected though the information cannot be leaked via the network to external persons. However, there is also physical security of the computer itself, and that where it gets interesting depending on who and what your trying to secure the pc from. If for instance the pc is sitting in a public area, and you are not worried just about external threats but also potential employee data theft then one should assume no information on the pc is secure even if the pc is standalone. ================================= Also - - - Just because a computer is CURRENTLY standalone, does not mean someone cannot decide to connect it to a network (with or without approval) - at which time it's no longer standalone. Few computers manufactured these days do not have networking capability built in. When a computer is disposed of, unless proper precautions are taken, all the information on it can be recovered - and misused - by whoever gets ahold of the hard drive.
Someone can attach a network printer to a standalone computer by using a USB connection. Using a cord to attach the printer to the computer, then installing the printer software, someone can then use the printer from the computer.
It's a standalone device, it doesn't need a computer.
An intrusion, or attack
"Virus intrusion software for your computer varies in price, depending on the sophistication of the intrusion detection and the ability to constantly update to protect against new threats. Expect to pay anywhere from $50 to $250 for software to protect your home computer."
The Microsoft Standalone Sweeper is a bootable anti-virus software that allows you to remove viruses that prevent your computer from booting properly.
Standalone Operating System
A computer is a computer even if it's not connected to anything. But it's usually referred to a "Stand-Alone" device. Additionally, if a computer is NOT part of any particular domain, it's default "domain" (at least for windows) is WORKGROUP.
An intrusion prevention system, as the name suggests, is a computer network appliance that prevents network access to individuals or viruses that are deemed to have malicious intentions.
Virtual Machine
In order to secure a host name for your computer, it is important to have internet hooked into the computer. Then a host name will be assigned to the computer