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Abstract. QR (Quick Response) codes are two-dimensional barcodes with the ability to encode different types of information. Because of their high information density and robustness, QR codes have gained popularity in various fields of application. Even though they offer a broad range of advantages, QR codes pose significant security risks. Attackers can encode malicious links that lead e.g. to phishing sites. Such malicious QR codes can be printed on small stickers and replace benign ones on billboard advertisements. Although many real world examples of QR code based attacks have been reported in the media, only little research has been conducted in this field and almost no attention has been paid on the interplay of security and human-computer interaction. In this work, we describe the manifold use cases of QR codes. Furthermore, we analyze the most significant attack scenarios with respect to the specific use cases. Additionally, we systemize the research that has already been conducted and identified usable security and security awareness as the main research challenges. Finally we propose design requirements with respect to the QR code itself, the reader application and usability aspects in order to support further research into to making QR code processing both secure and usable.

Social networks such as Facebook, Twitter and Google+ have attracted millions of users in the last years. One of the most widely used social networks, Facebook, recently had an initial public offering (IPO) in May 2012, which was among the biggest in Internet technology. Forprofit and nonprofit organizations primarily use such platforms for target-oriented advertising and large-scale marketing campaigns. Social networks have attracted worldwide attention because of their potential to address millions of users and possible future customers. The potential of social networks is often misused by malicious users who extract sensitive private information of unaware users. One of the most common ways of performing a large-scale data harvesting attack is the use of fake profiles, where malicious users present themselves in profiles impersonating fictitious or real persons. The main goal of this research is to evaluate the implications of fake user profiles on Facebook. To do so, we established a comprehensive data harvesting attack, the social engineering experiment, and analyzed the interactions between fake profiles and regular users to eventually undermine the Facebook business model. Furthermore, privacy considerations are analyzed using focus groups. As a result of our work, we provided a set of countermeasures to increase the awareness of users.

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HTTPS is one of the most important protocols used to secure communication and is, fortunately, becoming more pervasive. However, especially the long tail of websites is still not sufficiently secured. HTTPS involves different types of users, e.g., end users who are forced to make security decisions when faced with warnings or administrators who are required to deal with cryptographic fundamentals and complex decisions concerning compatibility.In this work, we present the first qualitative study of both end user and administrator mental models of HTTPS. We interviewed 18 end users and 12 administrators; our findings reveal misconceptions about security benefits and threat models from both groups. We identify protocol components that interfere with secure configurations and usage behavior and reveal differences between administrator and end user mental models.Our results suggest that end user mental models are more conceptual while administrator models are more protocol-based. We also found that end users often confuse encryption with authentication, significantly underestimate the security benefits of HTTPS. They also ignore and distrust security indicators while administrators often do not understand the interplay of functional protocol components. Based on the different mental models, we discuss implications and provide actionable recommendations for future designs of user interfaces and protocols.

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