Article Preview
Top1. Introduction And Background
In today’s world of globalization and borderless technology, the appearance of the Internet and the rapid development of telecommunication have made the world a global village. In the last decennium the e-mail service has become enormously used, and the principal vector of communication because it is cheap, reliable, fast and easily accessible. Moreover, it permits users with a mailbox (BAL) and address mail to exchange messages (picture, files, and text documents) from anywhere in the world via internet. Regrettably, this technology has led to the emergence and further escalation of several problems where among all the messages received by an individual in his mail box, we recognize two forms:
- •
HAM (Regular): The email (welcome) sent by friends or by websites subscribed in and meant for a specific person;
- •
SPAM (Irregular): The unsolicited emails (junk e-mail) sent in bulk to a large number of recipient indiscriminately and disingenuous, directly or indirectly by malicious people (scammers) that contains a payload (obvious or hidden) generally to hijack the recipient or for commercial interests.
The sending mechanism used by spammers are numerous such as: botnets, free email services, open proxies and stolen net blocks. The major tactics used by spammers to fool spam filters are: HTML tricks, Bayesian poisoning, multilingual email, content morphing, attachment image, forcing secondary MX, contouring IP reputation, or hiding the call to action (Hemalatha et al., 2015).
The nuisance brought by the spam is not limited only on the influx of undesired mails or the loss of legitimate mails; merely, we can identify different sorts of spam email such as Nigerian scam, FUD, Hoax, the spam telephony (Spim) and Phishing as illustrated in Figure 1. These forms of emails are annoying and the reasons for why users do not appreciate spam messages in their inbox are numerous: the waste overload in the mailbox that makes email less practical, loss of time in a business, time equals money, consumes a lot of network resource and bandwidth, loss of important emails, human resource consumption by damaging the computer if they contain virus, the risk of denial of service in the messenger server, and disruption of network operation. It is a rigorous phenomenon in the electronic life, which presents the main challenge and a security threat for Mail server administrators, and responsible of information organizations (Bouarara, 2015; Schieber & Hilbert, 2014). Generally an email is divided into two parts, namely, header (contain the identifier and the name of the sender) and body (the content of the email).
Figure 1. Several examples of spam email
According to the most recent report of the Radicati Group released in 2013 (Radicati, 2012), who supplies quantitative and qualitative researches with details on e-mail, security, and social networks. It has been illustrated that 70-80% of email traffic is composed of spam. More detail on this report are grouped in Table 1 and Figure 2.
Table 1. Radicati group statistic for email statistic
| Radicati Group Statistic |
| Email account active in the world | 2.9 trillion |
| People who use mail regularly | 2.4 billion |
| Number of mail sent in this years | 67 trillion |
| The average of email sent every day | 182.9 billion |
| The percentage of spam mail | 81% |
| Spam cost to all U.S. Corporations | 9.4 billion $ |
| Person who changed their email due to spam | 16% |
| Multilingual spam emails (emails written with different language) | 43% of all the spam emails are multilingual. |