The capabilities of modern devices, coupled with the almost ubiquitous availability of
Internet connectivity, have resulted in photos being shared online at an unprecedented …

Since their inception, captchas have been widely used for preventing fraudsters from
performing illicit actions. Nevertheless, economic incentives have resulted in an arms race …

In this paper, we focus on authentication and authorization flaws in web apps that enable
partial or full access to user accounts. Specifically, we develop a novel fully automated black …

The ever-increasing volumes of social knowledge shared in online social networks, the
establishment of trustworthy social relationships over these platforms, and the emergence of …

Location-based social networks (LBSNs) feature friend discovery by location proximity that
has attracted hundreds of millions of users world-wide. While leading LBSN providers claim …

As users navigate the web they face a multitude of threats; among them, attacks that result in
account compromise can be particularly devastating. In a world fraught with data breaches …

CAPTCHA stands for Completely Automated Public Turing Test to Tell Computers and
Human Apart. CAPTCHA is used for internet security. A few CAPTCHA schemes are …

In this paper, we introduce a novel approach to bypass modern face authentication systems.
More specifically, by leveraging a handful of pictures of the target user taken from social …

Fallback authentication, the process of re-establishing access to an account when the
primary authenticator is unavailable, holds critical significance. Approaches range from …

The advent of end-to-end encrypted (E2EE) messaging and backup services has brought
new challenges for usable authentication. Compared to regular web services, the nature of …