In the layman's world, often everything unusual that happens to a computer is believed to be caused by a "mysterious virus." In fact, however, most computer-related problems are caused by anything but a computer virus. As a result, IT departments tend to be less and less paranoid, and when real infections explode, they are initially skeptical and waste time. This is the proverbial "crying wolf" situation.
Another problem is that people believe that for something to be classified as a "computer virus," it needs to destroy user data, such as reformatting the hard disk. People often do not understand why someone would write a program that "only replicates." In fact, the majority of computer viruses do nothing but replicate. Many proof-of-concept viruses belong to this class, such as the WM/Concept virus. Such viruses might carry a message that is never displayed and is usually left for people who are expected to discover the virus, such as virus researchers. The most boring viruses do not contain any text other than replication code.
Virus replication, however, has many side effects. This includes the possibility of accidental data loss when the machine crashes due to a bug in the virus code or accidental overwriting of a part of the disk with relevant data.
Virus researchers call this kind of virus a no payload virus. However, there is no such thing as a harmless virus. By itself, the replication of the virus can be extremely annoying to the user. I have never met more than a few users who have said to me, "Oh, no problem about these three viruses. They just infect files. I can live with them on my system." Such thinking seems to be very unusual. Most people feel very stressed by computer virus infections for fear of data loss, among other things. Removal of the virus code can be very costly. For example, when a large software or hardware manufacturing company gets hit by a computer virus, the production of new systems must be stopped, causing millions of dollars of damage during every nonproductive day.