Shoulder surfing refers to observing someone's device screen without their consent. Conspicuously switching off the screen upon noticing a friend observing private messages may create an embarrassing situation. Initial evidence indicates that users adopt strategies to mitigate shoulder surfing based on their relationship to the observer. However, the social implications of such mitigation strategies remain largely unexplored. We present findings from an interview study with 12 participants to address this. We analyze experiences with shoulder surfers of different relationships to the user and collect feedback on eleven state-of-the-arts strategies for mitigating shoulder surfing. We show that the user-observer relationship impacts the choice of mitigation methods and that users often do not want observers to know they were caught. Based on our results, we conclude with implications for designing socially acceptable privacy protection mechanisms on mobile devices. CCS Concepts: • Security and privacy → Human and societal aspects of security and privacy.

There are many contexts in which a person's face needs to be obfuscated for privacy, such as in social media posts. We present a user-centered analysis of the effectiveness of DeepFakes for obfuscation using synthetically generated faces, and compare it with state-of-the-art obfuscation methods: blurring, masking, pixelating, and replacement with avatars. For this, we conducted an online survey (N=110) and found that DeepFake obfuscation is a viable alternative to state-of-the-art obfuscation methods; it is as effective as masking and avatar obfuscation in concealing the identities of individuals in photos. At the same time, DeepFakes blend well with surroundings and are as aesthetically pleasing as blurring and pixelating. We discuss how DeepFake obfuscation can enhance privacy protection without negatively impacting the photo's aesthetics. CCS CONCEPTS• Human-centered computing → Empirical studies in HCI.

Contact Tracing Apps (CTAs) have been developed and deployed in various parts of the world to track the spread of COVID-19. However, low social acceptance and the lack of adoption can impact CTA effectiveness. Prior work primarily focused on the privacy and security of CTAs, compared different models, and studied their app design. However, it remains unclear (1) how CTA privacy is perceived by end-users; (2) what reasons behind low adoption rates are, and ( 3) what the situation around the social acceptability of CTAs is. In this paper, we investigate these aspects by surveying 80 participants (40 from Australia, 40 from France). Our study reveals interesting results on CTA usage, experiences, and user perceptions. We found that privacy concerns, tech unawareness, app requisites, and mistrust can reduce the users' willingness to use CTAs. We conclude by presenting ways to foster public trust and meet users' privacy expectations that in turn support CTA's adoption.

Figure 1: The figure shows some commonly occurring scenarios of shoulder surfing in everyday life of users resulting from the findings of the diary study. The diary study showed that user's privacy is compromised in the naturalistic settings. Contentbased shoulder surfing is more frequent than authentication-based shoulder surfing. In the scenarios shown in the figure, the shoulder surfer (the person in the red shirt) is invading the user's privacy by observing the user's screen without their consent. Shoulder surfing can happen in private and/or public environments such as an individual's home, office, or shopping mall. Further, anyone could be a shoulder surfer; related or unrelated to the user, as it only requires observing someone's screen close in distance. Different observations are perceived differently by users, and users prefer different mechanisms in different contexts of shoulder surfing. (The figure was created using Canva [7] under Free Content License.