Tor anonymity network to shrink as a result of Heartbleed flaw

The Tor Project banned 380 vulnerable entry and exit relays and is eyeing 1,000 more

The Tor Project has flagged 380 Tor relays vulnerable to the critical Heartbleed flaw to be rejected from the Tor anonymity network, reducing the network's entry and exit capacity.

The decision has already been implemented on a Tor directory authority -- a server that maintains a list of Tor relays -- controlled by Roger Dingledine, the Tor Project leader, and is likely to be followed by other directory authority operators.

The 380 relays flagged for rejection are trusted entry relays, also known as guards, and exit relays. As a result, the immediate impact of this decision would be a 12 percent reduction in the network's guard and exit capacity, Dingledine said Wednesday in an email sent to the tor-relays mailing list.

Traffic from clients typically flows through the Tor network in three hops. The first hop is through a guard relay and the final hop, before the traffic is returned on the Internet to reach its intended destination, is through an exit relay.

Twelve percent might not sound like much, but guard and exit relays play an important role on the network and are not easy to replace. Many relays are run by volunteers, but they need to be trusted and need to have enough bandwidth at their disposal to handle traffic from multiple clients.

"I thought for a while about taking away their Valid flag rather than rejecting them outright, but this way they'll get notices in their logs," Dingledine said.

It seems that the ban might be permanent. Dingledine said that he wouldn't want those relays back on the Tor network even if they upgraded their versions of OpenSSL because their operators didn't patch the flaw in a timely manner.

The Heartbleed vulnerability was announced on Apr. 7 and affects versions 1.0.1 through 1.0.1f of OpenSSL, a library that implements the TLS (Transport Layer Security) encrypted communication protocol and which is used by many operating systems, web servers, browsers and other desktop and mobile applications.

The flaw allows attackers to extract information from the memory of an application that relies on OpenSSL for TLS communications, whether that application acts as a client or a server.

Both the Tor client and relay software is potentially vulnerable if the OpenSSL library is not updated on the underlying OS.

"Tor relays and bridges could maybe be made to leak their medium-term onion keys (rotated once a week), or their long-term relay identity keys," Dingledine wrote in a blog post last week after the Heartbleed flaw was announced.

"An attacker who has your relay identity key, has your onion key, and can intercept traffic flows to your IP address can impersonate your relay (but remember that Tor's multi-hop design means that attacking just one relay in the client's path is not very useful). In any case, best practice would be to update your OpenSSL package, discard all the files in keys/ in your DataDirectory, and restart your Tor to generate new keys."

In addition to the 380 guard and exit relays that have been banned already there are over 1,000 other relays that are also vulnerable and should be added to the rejection list at some point soon, Dingledine said.

Join the CSO newsletter!

Error: Please check your email address.

Tags patchesonline safetysecuritypatch managementTOR Projectencryptionprivacy

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Lucian Constantin

Latest Videos

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts