There is also the question of if it is definitely an intentional DDoS or if SR is just too popular for Tor to handle. At least one other really popular hidden service, with hundreds of Tor users, simply could not scale any larger with a single hidden service. They were not being DDoSed by an attacker, but their introduction points were so overloaded by their legitimate users that hardly anybody could connect with the .onion anymore. Although in their case they had people who could connect still, if absolutely nobody can connect to the silk road market then it is probably an intentional DDoS. If it has 100 people able to connect, and 400 who cannot connect, then it has very likely just gotten more popular than Tor can handle. In either case increasing the number of introduction nodes will alleviate the issue, but unfortunately if there is an attacker they can probably take down a lot of introduction nodes. If they have a Botnet they can probably exhaust the processing power of the entire Tor network .