Date Added: Jan 2010
Modern SMTP servers apply a variety of mechanisms to stem the volume of spam delivered to users. These techniques can be broadly classified into two categories: pre-acceptance approaches, which apply prior to a message being accepted (e.g. IP reputation), and post-acceptance techniques which apply after a message has been accepted (e.g. Content based signatures). The authors argue that the effectiveness of these measures varies based on the SMTP sender type. This paper focuses on the most light-weight pre-acceptance filtering mechanism - IP reputation.