Spam is information crafted to be delivered to a large number of recipients, in spite of their
wishes. A spam filter is an automated tool to recognize spam so as to prevent its delivery …

A recent study has found that malicious bots generated nearly a quarter of overall website
traffic in 2019 [102]. These malicious bots perform activities such as price and content …

Despite growing interest, there is a shortage of research about the methods and challenges
that concern researching ephemeral digital content. To fill this gap, the article discusses two …

The term big data encompasses a wide range of approaches of collecting and analyzing
data in ways that were not possible before the era of modern personal computing. One …

We carry out a systematic study of existing visual CAPTCHAs based on distorted characters
that are augmented with anti-segmentation techniques. Applying a systematic evaluation …

Despite several attacks have been proposed, text-based CAPTCHAs are still being widely
used as a security mechanism. One of the reasons for the pervasive use of text captchas is …

CAPTCHA is now almost a standard security technology. The most widely deployed
CAPTCHAs are text-based schemes, which typically require users to solve a text recognition …

Captchas are designed to be easy for humans but hard for machines. However, most recent
research has focused only on making them hard for machines. In this paper, we present …

Over the last decade, it has become well-established that a captcha's ability to withstand
automated solving lies in the difficulty of segmenting the image into individual characters …

Many security primitives are based on hard mathematical problems. Using hard AI problems
for security is emerging as an exciting new paradigm, but has been under-explored. In this …