An effective defense against email spam laundering

Mengjun Xie, Heng Yin, Haining Wang

Research output: Contribution to journalConference article

24 Scopus citations


Laundering email spam through open-proxies or compromised PCs is a widely-used trick to conceal real spam sources and reduce spamming cost in underground email spam industry. Spammers have been plaguing the Internet by exploiting a large number of spam proxies. The facility of breaking spam laundering and deterring spamming activities close to their sources, which would greatly benefit not only email users but also victim ISPs, is in great demand but still missing. In this paper, we reveal one salient characteristic of proxy-based spamming activities, namely packet symmetry, by analyzing protocol semantics and timing causality. Based on the packet symmetry exhibited in spam laundering, we propose a simple and effective technique, DBSpam, to on-line detect and break spam laundering activities inside a customer network. Monitoring the bi-directional traffic passing through a network gateway, DBSpam utilizes a simple statistical method, Sequential Probability Ratio Test, to detect the occurrence of spam laundering in a timely manner. To balance the goals of promptness and accuracy, we introduce a noise-reduction technique in DBSpam, after which the laundering path can be identified more accurately. Then, DBSpam activates its spam suppressing mechanism to break the spam laundering. We implement a prototype of DBSpam based on libpcap, and validate its efficacy through both theoretical analyses and trace-based experiments.

Original languageEnglish (US)
Article number1180428
Pages (from-to)179-190
Number of pages12
JournalProceedings of the ACM Conference on Computer and Communications Security
StatePublished - Dec 1 2006
EventCCS 2006: 13th ACM Conference on Computer and Communications Security - Alexandria, VA, United States
Duration: Oct 30 2006Nov 3 2006


  • Proxy
  • SPRT
  • Spam

ASJC Scopus subject areas

  • Software
  • Computer Networks and Communications

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