TABLE OF CONTENTS The purpose of this chapter is to make a survey of the different techniques [1] which are currently used to defend against viruses. These techniques, though efficient, do not remove all the risks but will at best limit them. That is the reason why it is illusive to solely base an antiviral protection policy on the use of an antivirus software, how efficient it may be. We will present therefore the main computer "hygiene rules" which can be very effective when properly applied and judiciously combined with an antivirus software. Most of these rules are derived from the security models defined during the eighties.
The issue behind defense against viral infections (prevention, detection, eradication) is far more tricky to address and to deal with than it seems, beyond the theoretical results presented in Chapter 3. We will just consider these two following aspects, at least to illustrate our comments.
The first aspect is the notion of protection. The latter is only valid with reference to a specific environment, specific tests or techniques The theoretical complexity of viral detection compels us in practice to use probabilistic and statistical techniques which have their inherent error probalilities [2]. To make things clear, if the environment of reference and techniques change, the defense against viruses is bound to fail unless these new changes are taken into account. It is precisely this weakness that the virus writer will exploit. No single defense is best for all situations.
The second...
