In order to understand the never-ending fights between developers of anti-spam detection techniques and the spammers; it is important to have an insight of the history of spam mails. On May 3, 1978, Gary Thuerk, a marketing manager at Digital Equipment Corporation sent his first mass email to more than 400 customers over the Arpanet in order to promote and sell Digital's new T-Series of VAX systems (Streitfeld, 2003). In this regard, he said, “It's too much work to send everyone an e-mail. So we'll send one e-mail to everyone”. He said with pride, “I was the pioneer. I saw a new way of doing things.” As every coin has two sides, any technology too can be utilized for good and bad intention. At that time, Gary Thuerk would have never dreamt of this method of sending mails to emerge as an area of research in future. Gary Thuerk ended up getting crowned as the father of spam mails instead of the father of e-marketing. In the present scenario, the internet receives 2.5 billion pieces of spam a day by spiritual followers of Thuerk.
Top1.1. Introduction
Spam mail is also known as junk mail, unsolicited commercial email (UCE) or unsolicited bulk Email (UBE). It is named after Spam - a brand of canned precooked meat products, which is portrayed as tasting nasty, ubiquitous -as included in every dish and unavoidable in the Monty Python comedy sketch in 1970. Hence, the word Spam came to be transferred by analogy.
Technically, spam mail is defined as “Unsolicited, unwanted email that was sent indiscriminately, directly or indirectly, by a sender having no current relationship with the recipient” (Sanz, HidalgoGomez, & PerezCortizo, 2008). It exhibits following important properties:
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Unsolicited: The information in the mail is not at all important for the addressee.
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Unknown Sender: The sender is not known to the recipient.
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Massive: These are sent in batches to many receivers at the same time.
Spam would not be so bad, if it was not quite so voluminous, offensive and annoying (Dynamic web Solutions, 2016). Unfortunately, today it has become a prevalent problem in the Internet world. Unsolicited email marketing exploits spam e-mail for commercial purposes to deliver information about various products. Spam includes bogus offers that could cost us time and money. One such example is Jeremy Jaynes, one of the spammers who earned $24 million by selling fake goods, services, and pornography via spam. He was arrested in December 2003 and convicted in November 2004.
Typically spam offers some doubtful job offers, financial service, impotence treatments and invitations to pornographic web sites (Dynamic web Solutions, 2016). Figure 1 shows some of the sample spam mails from personal account which are collected during month of June 2016. Day by day, they are getting successful in convincing the people to respond to these fake offers. Recent survey shows that both educated and uneducated people are easily getting trapped in the fake offers contained in spam messages. Spam e-mail may also include malwares or other executable file attachments. In reality, most people can live without this constant barrage of offensive unsolicited e-mail (Dynamic web Solutions, 2016). Moreover, a quality and productive time of employees is wasted in reading and deleting these spam from their mail inbox, thus affecting organization’s time, productivity and bandwidth severely.
According to the Message Anti-Abuse Working Group, the amount of spam e-mails in the first half of 2014 was approximately 90% (Maawg, 2011) of the total e-mails. Figure 2 shows the spam volume over a period of one year from March 2014 to March 2015 as reported by Symantec (Symantec, 2014).
Figure 2. Spam messages vs Total messages (Symantec, 2014)
Top1.2. How Spammer Works?
Spam is produced and shaped by spammers; who belong to many different populations around the world such as, programmers, attackers, criminals, terrorists, bots, merchants, marketers, corrupt bankers, cops, lawyers, security professionals, and hackers. In reality, no one ever admits to being a spammer. Today’s spammers change the source continuously and send spam from multiple infected machines or servers. Shutting down or blocking few infected servers doesn’t affect the flow of spam to any great effect. Spammers work like revolutionary war soldiers making everybody think they're fighting an army of 5000, when it's really only five guys.
In a typical scenario, an advertising agency or promoter enters into an agreement with the spammer and the spammer in turn sends email advertisements to a group of unwary recipients. As sending the spam is economical than sending postal bulk mailings, this practice is followed by most of the promoters.