Anonymity and Monitoring: How to Monitor the Infrastructure of an Anonymity System

The Tor network is a widely deployed anonymity system on the Internet used by thousands of users every day. A basic monitoring system has been designed and implemented to allow long-term statistics, provide feedback to the interested user, and detect certain attacks on the network. The implementation has been added to TorStatus, a project to display the current state of the Tor network. During a period of six months, this monitoring system collected data, where information and patterns have been extracted and analyzed. Interestingly, the Tor network is very stable with more than half of all the servers located in Germany and the United States. The data also shows a sinusoidal pattern every 24 h in the total number of servers.