Multistage Email Spam Filtering Based on Three-Way Decisions

A ternary, three-way decision strategy to email spam filtering divides incoming emails into three folders, namely, a mail folder consisting of emails that we accept as being legitimate, a spam folder consisting of emails that we reject as being legitimate, and a third folder consisting of emails that we cannot accept nor reject based on available information. The introduction of the third folder enables us to reduce both acceptance and rejection errors. Many existing ternary approaches are essentially a single-stage process. In this paper, we propose a model of multistage three-way email spam filtering based on principles of granular computing and rough sets.