A cluster of Tor servers suffered an unexplained outage just after the Tor project issued a warning of a possible cyber attack against the Tor network. Only certainty is someone physically accessed servers. Tor Project leader Roger Dingledine said the system is already built to be redundant so that users maintain anonymity even if the network is attacked. The stability of the overall Tor network depends in the Directory Authorities (DA) at least 5-6 Directory Authorities must be operational to keep the network updated and operating. An operator of a large cluster of servers in the Netherlands warned of a suspicious activity overnight on the servers.”]
Source: https://securityaffairs.co/wordpress/31429/hacking/who-hacked-a-cluster-tor-servers.html