For a week in March, Website security firm CloudFlare analyzed the traffic hitting its customers' sites from the anonymous Tor network.
The results of the study illustrate the double-edged nature of online anonymity. The Tor network—a peer-to-peer collection of volunteered servers linked together to create an anonymizing Web service—allows people in repressive countries to surf the Internet, enables activists to communicate freely and helps journalists evade government surveillance.
Yet, it also allows criminals to act with little fear of repercussions, because circumventing the anonymity provided by Tor is difficult, albeit not impossible.
In this case, the company found that nearly 94 percent of requests to CloudFlare customers' Web sites coming from the Tor network were automated and malicious—with comment spam, vulnerability scanning, advertising click-fraud, content scraping and brute-force log-in attempts topping the list of attacks coming from the network.
Because these types of attacks produce a lot of requests, a small number of attackers can use automation to create a large footprint, Matthew Prince, co-founder and CEO of CloudFlare, told eWEEK.
"It doesn't mean that 94 percent of users are bad, or that 94 percent of Tor traffic is bad," he said. "It is a very small universe of bad actors that is causing this large problem for our customers."
The Tor Project, the nonprofit foundation that maintains and develops Tor client and server software, criticized CloudFlare's approach to Web security. Tor users have complained that sites that use CloudFlare often throw up CAPTCHAs—automated tests to detect whether a visitor is a human or a bot—that can block people from reaching those sites, Mike Perry, Tor browser and Tor performance developer, stated in a blog post responding to the CloudFlare data.
"We suspect this figure is based on a flawed methodology by which CloudFlare labels all traffic from an IP address that has ever sent spam as 'malicious,' ” he wrote. “Tor IP addresses are conduits for millions of people who are then blocked from reaching websites under CloudFlare's system."
CloudFlare's Prince rebutted Perry's assertion, but offered only general points about how the company measures bots online, saying that the company uses a variety of techniques to determine whether a request is from an automated source, including creating content that is visible only to bots and turning off CloudFlare protections on certain Internet servers to use as controls.
The CloudFlare study is unlikely to settle the debate over the relative benefits and drawbacks of the Tor network. The network, created in the ’90s by a group of researchers and computer scientists affiliated with the U.S. Department of Defense, was originally conceived as a way to hide the Internet addresses of U.S. intelligence gatherers, so that their systems would not automatically be blocked. Because hiding in a crowd of users works only if there is a crowd of users, the U.S. government—through grants from the National Science Foundation—continues to support the project. Currently, there are about 2 million daily Tor users.
The benefits of the Tor Network rarely garner media attention, however. Instead, coverage is dominated by new reports of the more seedy side of the anonymity network, the so-called Dark Net. These include the takedown of online bazaars for drugs and illegal goods—such as the Silk Road markets, the shuttering of child porn rings using Tor, and the use of the network for malware communications.