A Review of Tor Network: Network structure, attacks and Filtering and confrontation techniques

The Tor network is one of the most useful and popular anonymity systems used on the web. This network works with bandwidths which volunteers provide from all around the world. By increasing the importance of security issues, surfing on the web anonymously in recent years attracted many users to Tor network and therefore it has been under a lot of research studies. Many of these studies have been implemented as attacks and in many cases the research itself also offers a solution for the problem too. Other important issue is bypassing filtering of internet in many countries by using Tor. It is a reason to filter Tor in these countries. In this paper we first review Tor network structure and then we categorize and explain attacks which are applied on the network. Finally we introduce how the network has been blocked in some countries and we also explain how Tor counteracted these filtering techniques.