On-line spam filter fusion

We show that a set of independently developed spam filters may be combined in simple ways to provide substantially better filtering than any of the individual filters. The results of fifty-three spam filters evaluated at the TREC 2005 Spam Track were combined post-hoc so as to simulate the parallel on-line operation of the filters. The combined results were evaluated using the TREC methodology, yielding more than a factor of two improvement over the best filter. The simplest method – averaging the binary classifications returned by the individual filters – yields a remarkably good result. A new method – averaging log-odds estimates based on the scores returned by the individual filters – yields a somewhat better result, and provides input to SVM- and logistic-regression-based stacking methods. The stacking methods appear to provide further improvement, but only for very large corpora. Of the stacking methods, logistic regression yields the better result. Finally, we ...

• Type: Conference
• Year: 2006
• Where: SIGIR
• Authors: Thomas R. Lynam, Gordon V. Cormack, David R. Cheriton
• Keywords: Individual filter, SIGIR 2006, Spam filters, Stacking Methods