Sunday, November 22, 2009

Not-a-Bot: Improving Service Availability in the Face of Botnet Attacks

Summary:

This paper introduces a Botnet detection and filtering mechanism called Not-a-Bot (NAB) which potentially can help internet systems distinguish between human generated request versus fake requests. NAB works by trying to authenticate the valid human-generated traffic at the source of the request by a trusted Attester module and further using a verifier module at the server to filter the requests.

The Attester is built on top of the Trusted Platform Module (TPM) (which is a secure cryptoprocessor, supposedly available in many of the computer platforms today). The verification of human generated traffic is done by correlating the mouse or keyboard activities with the generated traffic. This causes the most effective malicious Botnets to only be able to generate traffic at the human activity rate.

The three distinct application of NAB are spam mitigation, DDoS mitigation and Click-fraud mitigation. The authors are able to demonstrate the effectiveness of NAB under the tested scenarios through experiments. For example they show for spam mitigation scenario in which the ISP requires all the outgoing messages to be attested, NAB can cut down the forwarded spam (false negatives) by 92% while 0.08% false misclassification of human generated traffic.

Critique:

It seems like by deploying the NAB system, non-NAB users can potentially suffer from unfair access and prioritization. It can be interesting to discuss and understand to what degree non-attested human generated traffic might be in disadvantage?

In addition, it seems like a sophisticated Botnet can produce traffic at the rate of human activities. What would be the difference of NAB and a simpler verifier that checks at the servers weather the received traffic from the source is too high rate to be a human generated traffic. I believe this is a standard malicious attack detection and I couldn't really figure out the advantage of NAB in this case.

In overall, I vote for dropping this paper from the syllabus mainly for the reason that it is probably better suited for a network security class. Students who don't have much security background (like me) will probably have hard time understanding and further criticizing the paper.

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