Picture an unsuspecting scientist, hot on the research trail, looking for information that's readily available on one of the many computer bulletin boards used for scientific information searches. He flips on his computer and modem, dials into a bulletin board, finds the information, and downloads it onto a floppy disk. Chances are that he's just saved hours of precious library or lab time by using the bulletin board.
But the next time he accesses that disk, he may discover he has acquired an unwanted visitor, a terrorist of sorts that could destroy all of his hard work--a computer virus. Worse yet, if he has gotten the kind of virus that is instructed to activate itself at some date in the future, he may not know he has a virus until some damage has been done--which could be months after he uses the disk. That happened last December with the "Christmas ...