  Spam!: that's what Lorrie Faith Cranor and Brian LaMacchia exclaimed in the
title of a popular call-to-action article that appeared twenty years ago on
Communications of the ACM. 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 (e.g., 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.
