Pierluigi Paganini April 03, 2016

Experts at CloudFlare revealed that 94 percent of the Tor traffic they see is “per se malicious,” but Tor Project opposes it.

The experts from the Content delivery network (CDN) CloudFlare revealed that 94 percent of the Tor traffic they ordinary see is “malicious.”

It is not a mystery that Tor is becoming a favored tool of cyber criminals so many websites are blocking Tor users or degrading the services they receive, and CloudFlare has analyzed this issue in a blog post entitled “The Trouble with Tor.”

CloudFlare is not condemning the Tor network, in the post it highlights its importance for Anonymity online.

“Based on data across the CloudFlare network, 94% of requests that we see across the Tor network are per se malicious.” wrote Matthew Prince, the CloudFlare CEO.

A large portion of traffic on the Tor Network is generated by illegal activities that harm Internet users, for example according to data provided by Project Honey Pot, 18% of global email spam, roughly 6.5 trillion unwanted messages per year, begin with an automated bot harvesting email addresses via the Tor network. In

In response to a large number of websites adopt many types of restrictions for Tor users like the CAPTCHA verification.

“That doesn’t mean they are visiting controversial content, but instead that they are automated requests designed to harm our customers. A large percentage of the comment spam, vulnerability scanning, ad click fraud, content scraping, and login scanning comes via the Tor network.” continues Prince.

CloudFlare allows its customers to choose how they want to handle the traffic coming from Tor, they can whitelist all Tor traffic, block all traffic, use CAPTCHAs, or use a JavaScript challenge that checks the user’s browser.

Experts at CloudFlare believe that users will have two long term solutions, create a Tor version of their website that will accept only Tor traffic, or get the Tor Browser to make the distinction between human and automated traffic.

So What’s Next?

CloudFlare is working to reduce problems of navigation for the Tor users, limiting for example, the impact of CAPTCHAs.

“CloudFlare is working to reduce the impact of CAPTCHAs on Tor users without in any way compromising their anonymity and without exposing our customers to additional risk. Over the coming weeks and months we will roll out changes designed to make the lives of legitimate Tor Browser users easier while keeping our customers safe,” Prince said.

In response to the data published by CloudFlare, the developers behind the Tor Project released the “Fact sheet,” a report that analyzed the impact of the CloudFlare actions on the Tor users.

The experts are accusing CloudFlare of blocking the access of Tor users to major websites, like Amnesty International.

In many cases, Tor users are displayed annoying CAPTCHAs that might get users surfing with unsafe browsers in revealing their location.

“On one hand, the problematic CAPTCHAs might get users to access websites via unsafe browsers that can reveal their location, which can represent a serious risk for human rights activists and other groups for which anonymity is crucial. On the other hand, new users might believe they are not using Tor correctly, which could lead to them abandoning Tor altogether.” states the Tor Project.

“CloudFlare’s CAPTCHA system results in de facto censorship, since Tor users either cannot access a site or are deterred from using a site because of the obstacles presented by the CAPTCHAs” the Tor Project said.

.@SwartzCr is probably a robot tho. #dontblocktor pic.twitter.com/jjh3PUpgF7

— Griffin Boyce (@abditum) 31 marzo 2016

The members of the Tor Project are disappointed with CloudFlare that ignored the issue at least since 2013.

The experts at the Tor Project have argued that the malicious Tor traffic seen by CloudFlare is generated by a “tiny fraction of the millions of daily Tor users.”

“While many Tor relays appear as “malicious” from CloudFlare’s point of view, the abuse is likely coming from a tiny fraction of the millions of daily Tor users” states the Tor Project.

“When a connection to a website travels over Tor, it will exit the network via one of the thousand exit relays set up by volunteers all over the world. The largest exit nodes transport more than 70,000 connections at a given moment. If a small number of these connections contains what CloudFlare qualifies as ‘malicious traffic’ (spam, typically), CloudFlare will consider any subsequent connection as ‘malicious’,” added the Tor Project“Because exit relays are picked (usually at random) by the Tor client, a single bad guy could have all relays qualified as transporting ‘malicious traffic’.”

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Pierluigi Paganini

(Security Affairs – Tor Traffic, CloudFlare)