Zendesk breach affects Tumblr/Pinterest/Twitter

Published: 2013-02-22
Last Updated: 2013-02-22 13:40:16 UTC
by Johannes Ullrich (Version: 1)
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Users of tumblr, and likely the other sites mentioned in the subject line, received an e-mail informing them of a breach of a company called "Zendesk". Like myself, you may not have heard of Zendesk before, but they appearantly process customer support e-mail for these sites, including like in the Tumblr case, e-mail to aliases like lawenforcement@ and legal@. According to Zendesk, the attacker retrieved email addresses and subject lines, not e-mail bodies. According to the Zendesk home page, there are many other namebrand companies that are using Zendesk, but the breach notification mentions only the three I listed in the subject.

Lessons learned:

  • yet another "internet chokepoint" nobody thought about. A company like Zendesk, dealing with customer support for several large internet properties is a great point to monitor and collect intelligence as well as spreading malware. None of this has happened here.
  • Limit confidential information in customer support e-mails. NEVER mention a password. But other information should be limited to what is necessary to describe the problem. Of course, this may have to include sensitive data (account numbers, software versions and configurations.


With all the "Bad stuff" happending, we dodged some bad bullets this week. The NBC compromisse only led users to a rather old exploit. This Zendesk exploit didn't get very far (no e-mail bodies). The Bit9 exploit, even though it lasted for 6 months or so, was only used against 3 targets. Facebook/Apple developer compromisse didn't lead to backdoored code (we hope).

I think in particular the use of a "lame" exploit in the NBC case kind of points to another problem: It was probably pretty easy to deface the site. 


Johannes B. Ullrich, Ph.D.
SANS Technology Institute

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