Abstract
A defensive mechanism, which encompasses a variety of services and protections, has been proposed by several researchers for many organizations to protect system resources from misuse. In the practical use of defensive mechanisms such as CAPTCHAs and spam filters, attackers and defenders exchange 'victories,' each celebrating (temporary) success in breaking and defending. In this paper, since most of these defensive mechanisms depend on a single algorithm as a defence mechanism, we present a confusion matrix that helps to understand how a defensive mechanism performs a correct/incorrect classification. Specifically, the expected results, of a defensive mechanism from the confusion matrix, lead to categorising defensive mechanisms into two main categories: Assertive and Predictive defensive mechanisms. Moreover, the predicted results of a predictive defensive mechanism can be divided into two types: Interactive and non-Interactive defensive mechanisms. The result of this categorization scheme is useful to interested parties such as researchers, defensive mechanism designers and developers, as a tool to classify a defensive mechanism. Also, the view of interactive defensive mechanisms (IDMs) is important and useful, since it provides a consistent and clear understanding of the problem of IDMs in a system. Having such a view enables various interested parties, such as researchers, defensive mechanism design and defensive mechanism developers, to work from the same reference point, which is as unambiguous as possible.