Towards Practical Attacker Classification for Risk Analysis in Anonymous Communication

There are a number of attacker models in the area of anonymous communication. Most of them are either very simplified or pretty abstract – therefore difficult to generalize or even identify in real networks. While some papers distinct different attacker types, the usual approach is to present an anonymization technique and then to develop an attacker model for it in order to identify properties of the technique. Often such a model is abstract, unsystematic and it is not trivial to identify the exact threats for the end-user of the implemented system. This work follows another approach: we propose a classification of attacker types for the risk analysis and attacker modelling in anonymous communication independently of the concrete technique. The classes are designed in the way, that their meaning can be easily communicated to the end-users and management level. We claim that the use of this classification can lead to a more solid understanding of security provided by anonymizing networks, and therewith improve their development. Finally, we will classify some well known techniques and security issues according to the proposal and thus show the practical relevance and applicability of the proposed classification.