...messages, there was no initial ill intent with viruses. Rather than execute the malicious code they are now known for, earlyviruses were used as pranks -- silly messages would appear on the screen and then disappear. Over the years, these harmless...
http://www.technewsworld.com/rsstory/68067.html
...replicated by attaching itself to the Apple DOS 3.3 operating system passed around on floppy disks. Most of these earlyviruses were disk or file infectors and spread by file sharing. As wide-area computer networks (such as bulletin boards...
http://www.findwhitepapers.com/whitepaper2001/