The Onion Router (Tor) project has admitted that it has discovered relays which appear to have been targeting people who operate or access Tor hidden services.
According to a blog from the project, the attack involved modifying Tor protocol headers to do traffic confirmation attacks. The attacking “relays” joined the network on January 30th and they were removed on the 4th July. “While we don’t know when they started doing the attack, users who operated or accessed hidden services from early February through July 4 should assume they were affected,” it said.
The blog claimed it was unsure what was affected, but the attack did look for users who fetched and published hidden service descriptors, which would allow the attackers to learn the location of that hidden service, but attackers were not likely to be able to see any application-level traffic.
It is believed that the attacker used a traffic confirmation attack, when an attacker controls or observes the relays on both ends of a Tor circuit and then compares traffic timing, volume, or other characteristics to conclude that the two relays are indeed on the same circuit.
Commenting, Richard Cassidy, senior solutions architect for Alert Logic, said: “The recent exploits seen in earlier versions of the Tor application for browsers proves that the risk in using anonymity tools such as this is indeed high and, as users, we simply cannot guarantee the sovereignty or integrity of our data across these services.
“It is also clear that the data traversing Tor (and the users) is of high interest to governments (case in point: the recent news on a bounty offered to decrypt data sent over the Tor network by a government body), given its ability to allow users to circumnavigate many imposed censorship controls. This, in fact, is the main reason why Tor will quite clearly be the target (intensively so) of exploit attempts throughout 2014 and well into 2015 and why users should be extra careful on their activities when using Tor.”
Amichai Shulman, CTO of Imperva, said: “The quest for privacy is not what drives people to the Tor network; it is the desire to remain anonymous and untraceable when accessing certain applications or web sites, or when operating certain types of websites.
“Sadly the ideal of having a distributed, crowd based network for protecting free speech is largely abused by pirates (software and content) as well as evil-doers – from child pornography to drug trafficking and terrorism. This in turn makes the Tor network a target for all intelligence agencies as well as some domestic security organisations. I suspect the reported attack, targeted mostly at people who operate and access Tor hidden service, is of that origin.”
Fred Touchette, manager of security research at AppRiver, said: “Anytime anyone or anything on the internet steps into the light they immediately become targets, whether it be public scrutiny or all out attacks on its infrastructure. Given Tor’s claim of being a network where people can remain completely anonymous when setup and used properly, it’s no doubt that many saw that as a challenge.
“Ever since its conception people have been trying to find a way to de-anonymise the users of Tor. Oftentimes this was done to make it a stronger network and repair its issues, but other times it was in order to out its users. One such situation comes to mind and that’s the take down of The Silk
Road. The Feds spent plenty of time trying to crack the code before they were able to simply take control of the servers that hosted the site.”
Asked if this could be linked to recent claims that Governments want to break Tor, TK Keanini, CTO of Lancope, doubted this saying that despite the bounties placed on comprising Tor, or the endless amounts of threats made to subvert the technology, Tor is evolving and remains a target. “The Tor community is quick to react to incidents and this readiness is important to witness as there is a lot we can learn in how to be resilient despite a hostile and advanced threat,” he said.
Jaime Blasco, director of AlienVault Labs, said that Governments are actively investing a huge amount of money and resources in order to compromise the Tor network, and if you want to be secure, you should assume Tor is compromised and use other methods to maintain your anonymity and privacy within Tor.