Out-of-band discovery and evaluation for tor hidden services
Kang Li, Peipeng Liu, Qingfeng Tan, Jinqiao Shi, Yue Gao, Xuebin Wang · 2016
Tor is one of the most well-known anonymity networks that provides anonymity to service providers such as hidden web services. Recently size and content of Tor hidden services are highly concerned because of emerging illegal content. It is necesary to have discovery and analysis approaches to collect and analyze Tor hidden services. Previous in-band approaches are mostly based on the protocol and design principles of Tor network, which mostly have a great deal of resource consumption. In this paper, we propose an out-of-band approach to discover Tor hidden services, which is simpler and owns less resource consumption: using multiple search engines with specific keywords. In our experiments we collected 173667 unique .onion addresses in all using a single Amazon EC2 instances in 1 hour and found 4857 hidden web services online. We also propose a modified PageRank algrithm: OnionRank Algorithm to evaluate the importance of hidden web services, which concentrates more on Tor users' actions. Results showed that the top-ranking hidden web services are mostly famous in Tor network.