The History of Digital Spam

“Despite the tremendous efforts of the research community over the last two decades to mitigate this problem, the sense of urgency remains unchanged, as emerging technologies have brought new dangerous forms of digital spam under the spotlight.”

Communications of the ACM, August 2019, Vol. 62 No. 8, Pages 82-91
Review articles : The History of Digital Spam
By Emilio Ferrara

Spam! That’s what Lorrie Faith Cranor and Brian LaMacchia exclaimed in the title of a popular call-to-action article that appeared 20 years ago in Communications.10 And yet, despite the tremendous efforts of the research community over the last two decades to mitigate this problem, the sense of urgency remains unchanged, as emerging technologies have brought new dangerous forms of digital spam under the spotlight. Furthermore, when spam is carried out with the intent to deceive or influence at scale, it can alter the very fabric of society and our behavior. In this article, I will briefly review the history of digital spam: starting from its quintessential incarnation, spam emails, to modern-days forms of spam affecting the Web and social media, the survey will close by depicting future risks associated with spam and abuse of new technologies, including artificial intelligence (AI), for example, digital humans. After providing a taxonomy of spam, and its most popular applications emerged throughout the last two decades, I will review technological and regulatory approaches proposed in the literature, and suggest some possible solutions to tackle this ubiquitous digital epidemic moving forward.


An omni-comprehensive, universally acknowledged definition of digital spam is hard to formalize. Laws and regulation attempted to define particular forms of spam, for example, email (see 2003’s Controlling the Assault of Non-Solicited Pornography and Marketing Act.) However, nowadays, spam occurs in a variety of forms, and across different techno-social systems. Each domain may warrant a slight different definition that suits what spam is in that precise context: some features of spam in a domain, for example, volume in mass spam campaigns, may not apply to others, for example, carefully targeted phishing operations.

<p”>In an attempt to propose a general taxonomy, I here define digital spam as the attempt to abuse of, or manipulate, a techno-social system by producing and injecting unsolicited, and/or undesired content aimed at steering the behavior of humans or the system itself, at the direct or indirect, immediate or long-term advantage of the spammer(s).

This broad definition will allow me to track, in an inclusive manner, the evolution of digital spam across its most popular applications, starting from spam emails to modern-days spam. For each highlighted application domain, I will dive deep to understand the nuances of different digital spam strategies, including their intents and catalysts and, from a technical standpoint, how they are carried out and how they can be detected.


Wikipedia provides an extensive list of domains of application:


“While the most widely recognized form of spam is email spam, the term is applied to similar abuses in other media: instant messaging spam, Usenet news-group spam, Web search engine spam, spam in blogs, wiki spam, online classified ads spam, mobile phone messaging spam, Internet forum spam, junk fax transmissions, social spam, spam mobile apps, television advertising and file sharing spam.” (


The accompanying table summarizes a few examples of types of spam and relative context, including whereas there exist machine learning solutions (ML) to each problem. Email is known to be historically the first example of digital spam (see Figure 1) and remains uncontested in scale and pervasiveness with billions of spam emails generated every day.10 In the late 1990s, spam landed on instant messaging (IM) platforms (SPIM) starting from AIM (AOL Instant Messenger) and evolving through modern-days IM systems such as WhatsApp, Facebook Messenger, and WeChat. A widespread form of spam that emerged in the same period was Web search engine manipulation: content spam and link farms allowed spammers to boost the position of a target Website in the search result rankings of popular search engines, by gaming algorithms like PageRank and the like. With the success of the social Web, in the early 2000s we witnessed the rise of many new forms of spam, including Wiki spam (injecting spam links into Wikipedia pages), opinion and review spam (promoting or smearing products by generating fake online reviews), and mobile messaging spam (SMS and text messages sent directly to mobile devices). Ultimately, in the last decade, with the increasing pervasiveness of online social networks and the significant advancements in AI, new forms of spam involve social bots (accounts operated by software to interact at scale with social Web users), false news websites (to deliberately spread disinformation), and multi-media spam based on AI.


In the following, I will focus on three of these domains: email spam, Web spam (specifically, opinion spam and fake reviews), and social spam (with a focus on social bots). Furthermore, I will highlight the existence of a new form of spam that I will call AI spam. I will provide examples of spam in this new domain, and lay out the risks associated with it and possible mitigation strategies.


Four decades have passed since the first case of email spam was reported by 400 ARPANET users (see Figure 1). While some prominent computer scientists (including Bill Gates) thought that spam would quickly be solved and soon remembered as a problem of the past,10 we have witnessed its evolution in a variety of forms and environments. Spam feeds itself of (economic, political, ideological, among others) incentives and of new technologies, both of which there is no shortage of, and therefore it is likely to plague our society and our systems for the foreseeable future.


It is therefore the duty of the computing community to enact policies and research programs to keep fighting against the proliferation of current and new forms of spam. I conclude suggesting three maxims that may guide future efforts in this endeavor: …


 Figure 1: The History of Digital Spam 1898-2018 Click on image for full-size view.
Figure 1: The History of Digital Spam 1898-2018 Click on image for full-size view.

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About the Author:

Emilio Ferrara is an assistant research professor and associate director of Applied Data Science at the University of Southern California Information Sciences Institute, Marina Del Rey, CA, USA.


Author Emilio Ferrara discusses his article “The History of Digital Spam” from the August 2019 issue of Communications of the ACM.


Have you got anything without Spam in it?” – From “Monty Python’s Flying Circus” Series 2, Episode 12 from Monty Python on Facebook.

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