Time , bandwidth and memory resources are occupied to result in the link block as well as the deluge of unhealthy messages . currently , there are some mature filtering methods which adopt software automated filtering and user setting rules . most of the software has a constraint that they need manual setting , which requires some professional domain knowledge 目前已有一些比較成熟的過濾方法采用通過軟件自動過濾與用戶設定規(guī)則的方式,但這類軟件存在著明顯的不足:它需要人工設定過濾規(guī)則,這要求用戶或管理員有較強的專業(yè)知識,還要求用戶能隨著垃圾郵件情況的變化不斷調(diào)整這些規(guī)則。