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Mozilla puts old hardware to new use, runs Tor relays

Lucian Constantin | Jan. 30, 2015
Mozilla has dusted off some decommissioned servers and networking gear and used them to set up high-speed relays on the Tor anonymity network.

Mozilla has dusted off some decommissioned servers and networking gear and used them to set up high-speed relays on the Tor anonymity network.

The plan to run Tor relays was revealed in November, when the software developer announced its Polaris Privacy Initiative, a collaboration with other non-profit organizations to enhance privacy on the Web.

One of those organizations was the Tor Project, which develops the client and server software for the Tor anonymity network. As part of the partnership, Mozilla said that it will make some changes in Firefox to ease the work of Tor Project developers who maintain the Tor Browser, a modified version of Firefox that allows users to access the Web through the Tor network.

The organization also said at the time that it will host its own "high-capacity Tor middle relays to make Tor's network more responsive and allow Tor to serve more users."

On Wednesday, Mozilla announced that its prototype Tor relays are up and running on three HP ProLiant SL170z G6 servers connected to a pair of Juniper EX4200 switches that benefit from two 10Gbps uplinks through one of the organization's transit providers.

"The current design is fully redundant," Mozilla network engineer Arzhel Younsi said in a blog post that contains more details about the project. "This allows us to complete maintenance or have node failure without impacting 100% of traffic. The worst case scenario is a 50% loss of capacity."

The relays currently run outside of Mozilla's production infrastructure, but the organization's security team helped lock them down with strict firewall filtering, operating system hardening, automatic updates, network device management and more.

"We've also implemented a periodic security check to be run on these systems," Younsi said. "All of them are scanned from inside for security updates and outside for opened ports."

The Tor network has three main types of relays, or nodes: middle relays, exit relays and bridges. Internet traffic routed through the Tor network will randomly pass through at least three Tor relays before it exits back onto the Internet to reach its final destination.

Middle relays are responsible for passing data within the Tor network. Over time, middle relays can automatically become entry guard nodes as they build trust according to a network consensus algorithm — in fact one of Mozilla's middle relays has already become an entry guard. Entry guards serve as the first links between users and the Tor network.

At the other end are exit relays, which act as the last hops in the network and whose purpose is to send the traffic back on the Internet. A site that receives a request from a Tor user will see the request originating from the Internet Protocol (IP) address of a Tor exit relay, not the real IP address of the user.

 

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