Spam Filter Based on Dynamic Sender Policy Framework

The Sender Policy Framework (SPF) is an open standard specifying a technical method to prevent sender address forgery. This technique requires network administrators to create SPF records for their domains. A philosophic issue, which may limit the deployment of SPF, is that in order to use SPF, a network administrator needs to configure local DNS, but others, not himself, will take benefits from that configuration. Therefore, we proposed the Dynamic Sender Policy Framework (DSPF) approach, in which, the legal IP addresses of servers which send emails are collected and provided by a third-party. The database of SPF records can be updated automatically and can also be used among other email servers and email gateways. Using DSPF, clients may check the SPF records without any extra configuration of their DNS. Results showed that the system is able to filter 98% spam and 100% phishing. Collecting and updating processes of the database are described. Factors that influence database´s performance are discussed.