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Center for Education and Research in Information Assurance and Security

Cowed Through DNS

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May 2010 will mark the 4th aniversary of our collective cowing by spammers, malware authors and botnet operators. In 2006, spammers squashed Blue Frog. They made the vendor of this service, Blue Security, into lepers, as everyone became afraid of being contaminated by association and becoming a casualty of the spamming war. Blue Frog hit spammers were it counted -- in the revenue stream, simply by posting complaints to spamvertized web sites. It was effective enough to warrant retaliation. DNS was battered into making Blue Security unreachable. The then paying commercial clients of Blue Security were targetted, destroying the business model; so Blue Security folded [1]. I was stunned that the "bad guys" won by brute force and terror, and the security community either was powerless or let it go. Blue Security was even blamed for some of their actions and their approach. Blaming the victims for daring to organize and attempt to defend people, err, I mean for provoking the aggressor further, isn't new. An open-source project attempting to revive the Blue Frog technology evaporated within the year. The absence of interest and progress has since been scary (or scared) silence.

According to most sources, 90-95% of our email traffic has been spam for years now. Not content with this, they subject us to blog spam, friendme spam, IM spam, and XSS (cross-site scripting) spam. That spam or browser abuse through XSS convinces more people to visit links and install malware, thus enrolling computers into botnets. Botnets then enforce our submission by defeating Blue Security type efforts, and extort money from web-based businesses. We can then smugly blame "those idiots" who unknowingly handed over the control over their computers, with a slight air of exasperation. It may also be argued that there's more money to be made selling somewhat effective spam-fighting solutions than by emulating a doomed business model. But in reality, we've been cowed.

I had been hoping that the open source project could make it through the lack of a business model; after all, the open source movement seems like a liberating miracle. However, the DNS problem remained. So, even though I didn't use Blue Frog at the time, I have been hoping for almost 4 years now that DNS would be improved to resist the denial of service attacks that took Blue Security offline. I have been hoping that someone else would take up the challenge. However, all we have is modest success at (temporarily?) disabling particular botnets, semi-effective filtering, and mostly ineffective reporting. Since then, spammers have ruled the field practically uncontested.

Did you hear about Comcast's deployment of DNSSEC [2]? It sounds like a worthy improvement; it's DNS with security extensions, or "secure DNS". However, Denial-of-service (DoS) prevention is out-of-scope of DNSSEC! It has no DoS protections, and moreover there are reports of DoS "amplification attacks" exploiting the larger DNSSEC-aware response size [3]. Hum. Integrity is not the only problem with DNS! A search of IEEE Explore and the ACM digital library for "DNS DoS" reveals several relevant papers [4-7], including a DoS-resistant backwards compatible replacement for the current DNS from 2004. Another alternative, DNSCurve has protection for confidentiality, integrity and availability (DoS) [8], has just been deployed by OpenDNS [9] and is being proposed to the IETF DNSEXT working group [10]. This example of leadership suggests possibilities for meaningful challenges to organized internet crime. I will be eagerly watching for signs of progress in this area. We've kept our head low long enough.

References
1. Robert Lemos (2006) Blue Security folds under spammer's wrath. SecurityFocus. Accessed at http://www.securityfocus.com/news/11392
2. Comcast DNSSEC Information Center Accessed at http://www.dnssec.comcast.net/
3. Bernstein DJ (2009) High-speed cryptography, DNSSEC, and DNSCurve. Accessed at: http://cr.yp.to/talks/2009.08.11/slides.pdf
4. Fanglu Guo, Jiawu Chen, Tzi-cker Chiueh (2006) Spoof Detection for Preventing DoS Attacks against DNS Servers. 26th IEEE International Conference on Distributed Computing Systems.
5. Kambourakis G, Moschos T, Geneiatakis D, Gritzalis S (2007) A Fair Solution to DNS Amplification Attacks. Second International Workshop on Digital Forensics and Incident Analysis.
6. Hitesh Ballani, Paul Francis (2008) Mitigating DNS DoS attacks. Proceedings of the 15th ACM conference on Computer and communications security
7. Venugopalan Ramasubramanian, Emin Gün Sirer (2004) The design and implementation of a next generation name service for the internet. Proceedings of the 2004 conference on Applications, technologies, architectures, and protocols for computer communications
8. DNSCurve: Usable security for DNS (2009). Accessed at http://dnscurve.org/
9. Matthew Dempsky (2010) OpenDNS adopts DNSCurve. Accessed at http://blog.opendns.com/2010/02/23/opendns-dnscurve/
10. Matthew Dempsky (2010) [dnsext] DNSCurve Internet-Draft. Accessed at http://www.ops.ietf.org/lists/namedroppers/namedroppers.2010/msg00535.html

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