It is a joke, not a serious virus. Because its alleged destructive behaviour requires positive action by its intended human victim, the intended victim can simply not take the instructed action (deleting their own files). Those humans who follow the virus's instruction to forward it to others can be safely presumed to have not followed the destructive part of the instructions, and to be forwarding the message deliberately so that their friends may also appreciate the joke.
The joke is based on the perceived foolishness in the design of mail programs that are susceptible to viruses. A normal email virus works by including computer instructions in an email; the mail programs in question execute those instructions without an explicit request from the user. Most mail programs, in contrast, maintain a distinction between code and data, and so are immune to this type of virus. The honor system virus draws a parallel between humans and mail programs, and so makes the reader think about the human behaviours that are analogous to these mail program behaviours.
It should be noted that some serious email viruses make use of human action in their transmission. They include text that attempts to con the user into invoking the machine-executable part of the message. This is unlike the honor system virus not only because there is a directly machine-executable component but also because the virus attempts to mislead the human. The honor system virus is entirely straightforward and honest in its human-directed instructions, just like the computer-directed part of a normal email virus.
A signature virus is a piece of text placed in a signature block which encourages readers to copy it into their own signature block. Like their email cousins, they reproduce only by manual copying. A simple example:
Some signature viruses carry a short informational "payload" in addition to the copying instructions.
The honor system virus is also known as the Amish Computer Virus, manual virus, the Blond Computer Virus, the Irish Computer Virus, the Syrian Computer Virus, the Norwegian Computer Virus and the Unix Computer Virus.
The "Unix Computer Virus" name refers to the Unix family of operating systems. In addition to having mail programs that lack the deficiencies that allow viruses to spread by email, they make a relatively inhospitable environment for viruses, when compared to other operating systems popular on desktop computers. Viruses do occur on Unix-like systems, but they are far less common than in other environments. A corresponding variant of the honor system virus reads thus:
A "Mac OS 9 Virus" variant also circulated:
The "Discount Virus" variant apparently fooled some people into thinking they actually received a virus: