An effective multi-layered defense framework against spam

Spam is a big problem for email users, and more serious for wireless mobile users with limited bandwidth. The battle between spamming and anti-spamming technologies has been going on for many years. Though many advanced antispamming technologies are progressing significantly, spam is still able to bombard many email users. The problem worsens when some anti-spamming methods unintentionally filtered legitimate emails instead! In this paper, we first review existing anti-spam technologies, then propose a layered defense framework using a combination of anti-spamming methods. Under this framework, the server-level defense is targeted for common spam while the client-level defense further filters specific spam for individual users. This layered structure improves on filtering accuracy and yet reduces the number of false positives.