Two of the seven directory authority servers that the Tor Project uses to run its anonymous browsing service have been compromised, along with a new server that the project uses to host metrics and graphs. The project s organizers discovered the attack earlier this month and are advising users who run Tor nodes to upgrade to a new version of the software. The organizers said that there is no risk that the attackers could have matched Tor users to their browsing habits. It seems we were attacked for the capacity and bandwidth of the servers, and the servers also carry out functions for Tor.
Source: https://threatpost.com/tor-servers-hacked-012210/73413/