Increasing reliance on the electronic mail (e-mail) has attracted spammers to send more and more spam e-mails in order to maximizing their financial gains. These unwanted e-mails are not only clogging the Internet traffic but are also causing storage problems at the receiving servers. Besides these, spam e-mails also serve as a vehicle to a variety of online crimes and abuses. Although several anti-spam procedures are currently employed to distinguish spam e-mails from the legitimate e-mails yet spammers and phishes obfuscate their e-mail content to circumvent anti-spam procedures. Efficiency of anti-spam procedures to combat spam entry into the system greatly depend on their level of operation and a clear insight of various possible modes of spamming. In this paper we investigate directed graph model of Internet e-mail infrastructure and spamming modes used by spammers to inject spam into the system. The paper outlines the routes, system components, devices and protocols exploited by each spamming mode.
Shah, Nisar A. and Banday, M. Tariq, " System Analysis of SPAM" (2010). All Sprouts Content. 251.