ABL: An original active blacklist based on a modification of the SMTP
Pablo Marques De Oliveira, Mateus B. Vieira, Isaac C. Ferreira, João Paulo Leite, Edvard Martins de Oliveira, Bruno Tardiole Kuehne, Edmilson Marmo Moreira, Otávio A. S. Carpinteiro · arXiv (Cornell University) · 2022
This paper presents a novel Active Blacklist (ABL) based on a modification of the Simple Mail Transfer Protocol (SMTP). ABL was implemented in the Mail Transfer Agent (MTA) Postfix of the e-mail server Zimbra and assessed exhaustively in a series of experiments. The modified server Zimbra showed computational performance and costs similar to those of the original server Zimbra when receiving legitimate e-mails. When receiving spam, however, it showed better computing performance and costs than the original Zimbra. Moreover, there was a considerable computational cost on the spammer's server when it sent spam e-mails. ABL was assessed at the Federal University of Itajubá, Brazil, during a period of sixty-one days. It was responsible for rejecting a percentage of 20.94% of the spam e-mails received by the university during this period. After this period, it was deployed and remained in use, from July-2015 to July-2019, at the university. ABL is part of the new Open Machine-Learning-Based Anti-Spam (Open-MaLBAS). Both ABL and Open-MaLBAS are freely available on GitHub.