A Survey on Interdependent Privacy <s> Risks. <s> This article investigates Facebook users' awareness of privacy issues and perceived benefits and risks of utilizing Facebook. Research found that Facebook is deeply integrated in users' daily lives through specific routines and rituals. Users claimed to understand privacy issues, yet reported uploading large amounts of personal information. Risks to privacy invasion were ascribed more to others than to the self. However, users reporting privacy invasion were more likely to change privacy settings than those merely hearing about others' privacy invasions. Results suggest that this lax attitude may be based on a combination of high gratification, usage patterns, and a psychological mechanism similar to third-person effect. Safer use of social network services would thus require changes in user attitude. <s> BIB001 </s> A Survey on Interdependent Privacy <s> Risks. <s> Photo tagging is a popular feature of many social network sites that allows users to annotate uploaded images with those who are in them, explicitly linking the photo to each person's profile. In this paper, we examine privacy concerns and mechanisms surrounding these tagged images. Using a focus group, we explored the needs and concerns of users, resulting in a set of design considerations for tagged photo privacy. We then designed a privacy enhancing mechanism based on our findings, and validated it using a mixed methods approach. Our results identify the social tensions that tagging generates, and the needs of privacy tools to address the social implications of photo privacy management. <s> BIB002 </s> A Survey on Interdependent Privacy <s> Risks. <s> We investigate regrets associated with users' posts on a popular social networking site. Our findings are based on a series of interviews, user diaries, and online surveys involving 569 American Facebook users. Their regrets revolved around sensitive topics, content with strong sentiment, lies, and secrets. Our research reveals several possible causes of why users make posts that they later regret: (1) they want to be perceived in favorable ways, (2) they do not think about their reason for posting or the consequences of their posts, (3) they misjudge the culture and norms within their social circles, (4) they are in a "hot" state of high emotion when posting, or under the influence of drugs or alcohol, (5) their postings are seen by an unintended audience, (6) they do not foresee how their posts could be perceived by people within their intended audience, and (7) they misunderstand or misuse the Facebook platform. Some reported incidents had serious repercussions, such as breaking up relationships or job losses. We discuss methodological considerations in studying negative experiences associated with social networking posts, as well as ways of helping users of social networking sites avoid such regrets. <s> BIB003 </s> A Survey on Interdependent Privacy <s> Risks. <s> In this paper, we explore the risks of friends in social networks caused by their friendship patterns, by using real life social network data and starting from a previously defined risk model. Particularly, we observe that risks of friendships can be mined by analyzing users' attitude towards friends of friends. This allows us to give new insights into friendship and risk dynamics on social networks. <s> BIB004 </s> A Survey on Interdependent Privacy <s> Risks. <s> Social networks are becoming increasingly popular nowadays. Users share personal information about themselves and other users in order to build and maintain their social network. However, the large amount of personal information available on social networks poses risks of data misuse. Although social networks offer users the possibility to specify privacy settings to regulate access to their information, these settings are often complicated and unintuitive, especially when dealing with new modalities of social communication like tagging. In this paper we investigate the privacy consequences of information sharing in social networks. In particular, we formally analyze the impact of the privacy settings and the use of tagging in Facebook on the visibility of information. To increase users’ awareness of the risks of information sharing and empower users to control their information, we present a tool for determining the visibility of users’ information based on their privacy settings and tagging. <s> BIB005 </s> A Survey on Interdependent Privacy <s> Risks. <s> The amount of media uploaded to the Web is still rapidly expanding. The ease-of-use of modern smartphones in combination with the proliferation of high-speed mobile networks facilitates a culture of spontaneous and often carefree sharing of user-generated content, especially photos and videos. An increasing number of modern devices are capable of embedding location information and other metadata into created content. However, currently there is not much user awareness of possible privacy consequences of such data. While in most cases users upload their own media consciously, the flood of media uploaded by others is so huge that it is almost impossible for users to stay aware of all media that might be relevant to them. Current social network services and photo-sharing sites mainly focus on the privacy of users' own media in terms of access control, but offer few possibilities to deal with privacy implications created by other users' actions. We conducted an online survey with 414 participants. The results show that users would like to get more information about media shared by others. Based on an analysis of prevalent sharing services like Flickr, Facebook, or Google+ and an analysis of metadata of three different sets of crawled photos, we discuss privacy implications and potentials of the emerging trend of (geo-)tagged media. Finally, we present a novel concept on how location information can actually help users to control the flood of potentially infringing or interesting media. <s> BIB006 </s> A Survey on Interdependent Privacy <s> Risks. <s> The popularity of third-party apps on social network sites and mobile networks emphasizes the problem of the interdependency of privacy. It is caused by users installing apps that often collect and potentially misuse the personal information of users’ friends who are typically not involved in the decision-making process. In this paper, we provide an economic model and simulation results addressing this problem space. We study the adoption of social apps in a network where privacy consequences are interdependent. Motivated by research in behavioral economics, we extend the model to account for users’ other-regarding preferences; that is, users care about privacy harms they inflict on their peers. <s> BIB007 </s> A Survey on Interdependent Privacy <s> Risks. <s> The capabilities of modern devices, coupled with the almost ubiquitous availability of Internet connectivity, have resulted in photos being shared online at an unprecedented scale. This is further amplified by the popularity of social networks and the immediacy they offer in content sharing. Existing access control mechanisms are too coarse-grained to handle cases of conflicting interests between the users associated with a photo; stories of embarrassing or inappropriate photos being widely accessible have become quite common. In this paper, we propose to rethink access control when applied to photos, in a way that allows us to effectively prevent unwanted individuals from recognizing users in a photo. The core concept behind our approach is to change the granularity of access control from the level of the photo to that of a user's personally identifiable information (PII). In this work, we consider the face as the PII. When another user attempts to access a photo, the system determines which faces the user does not have the permission to view, and presents the photo with the restricted faces blurred out. Our system takes advantage of the existing face recognition functionality of social networks, and can interoperate with the current photo-level access control mechanisms. We implement a proof-of-concept application for Facebook, and demonstrate that the performance overhead of our approach is minimal. We also conduct a user study to evaluate the privacy offered by our approach, and find that it effectively prevents users from identifying their contacts in 87.35% of the restricted photos. Finally, our study reveals the misconceptions about the privacy offered by existing mechanisms, and demonstrates that users are positive towards the adoption of an intuitive, straightforward access control mechanism that allows them to manage the visibility of their face in published photos. <s> BIB008 </s> A Survey on Interdependent Privacy <s> Risks. <s> Online social networks greatly facilitate social exchange among friends. At times, for amusement, individuals may be targeted by friends’ playful teases, which often involve exposing individuals’ private embarrassing information, such as information that reveals their past indecent behavior, mischief, or clumsiness. Although individuals sometimes do enjoy the humor, they might also be offended by the involuntary exposure. Drawing on social exchange theory, this paper elucidates the consequences of an embarrassing exposure in online social networks. Specifically, this study examines the effects of information dissemination and network commonality on individuals’ exchange assessment as well as how this assessment shapes their behavioral responses. The results of our experiment provide strong evidence that information dissemination and network commonality jointly influence individuals’ perceived privacy invasion and perceived relationship bonding. In addition, whereas perceived privacy invasion increases tra... <s> BIB009 </s> A Survey on Interdependent Privacy <s> Risks. <s> In online social networks, because one's private information can be co-owned and disclosed by peers, a new type of privacy concern, i.e., information privacy concern about peer disclosure (IPCPD), looms large. Should a member of an online social network be offered decision control to veto ex-ante the disclosure of his/her information by peers? There has been no theoretical research on the effectiveness of decisional control to alleviate such a privacy concern. Drawing on the communication privacy management perspective and the impression management theory, this study proposes a three-way interaction effect among three important antecedents of IPCPD: 1) decisional control; 2) image discrepancy (i.e., the degree to which the disclosed information portrays an unfavorable image of the disclosed person); and 3) social network overlap between the disclosed person and the discloser. Our experimental study reveals significant findings. When image discrepancy is low, decisional control is helpful only when the social network overlap between the disclosed one and the discloser is low. When image discrepancy is high, decisional control is helpful only when the social network overlap between the disclosed one and the discloser is high. This study contributes to a theory of privacy concern about peer disclosure in the context of online social networks. <s> BIB010 </s> A Survey on Interdependent Privacy <s> Risks. <s> Third-party apps enable a personalized experience on social networking platforms; however, they give rise to privacy interdependence issues. Apps installed by a user’s friends can collect and potentially misuse her personal data inflicting collateral damage on the user while leaving her without proper means of control. In this paper, we present a multi-faceted study on the collateral information collection of apps in social networks. We conduct a user survey and show that Facebook users are concerned about this issue and the lack of mechanisms to control it. Based on real data, we compute the likelihood of collateral information collection affecting users; we show that the probability is significant and depends on both the friendship network and the popularity of the app. We also show its significance by computing the proportion of exposed user attributes including the case of profiling, when several apps are offered by the same provider. Finally, we propose a privacy dashboard concept enabling users to control the collateral damage. <s> BIB011 </s> A Survey on Interdependent Privacy <s> Risks. <s> AbstractAcademic studies typically view privacy threats as originating solely from organizations. With the rise of social media, such a view is incomplete because consumers increasingly face risks ... <s> BIB012 </s> A Survey on Interdependent Privacy <s> Risks. <s> Abstract Third-party applications on Facebook can collect personal data of the users who install them, but also of their friends. This raises serious privacy issues as these friends are not notified by the applications nor by Facebook and they have not given consent. This paper presents a detailed multi-faceted study on the collateral information collection of the applications on Facebook. To investigate the views of the users, we designed a questionnaire and collected the responses of 114 participants. The results show that participants are concerned about the collateral information collection and in particular about the lack of notification and of mechanisms to control the data collection. Based on real data, we compute the likelihood of collateral information collection affecting users: we show that the probability is significant and greater than 80% for popular applications such as TripAdvisor. We also demonstrate that a substantial amount of profile data can be collected by applications, which enables application providers to profile users. To investigate whether collateral information collection is an issue to users’ privacy we analysed the legal framework in light of the General Data Protection Regulation. We provide a detailed analysis of the entities involved and investigate which entity is accountable for the collateral information collection. To provide countermeasures, we propose a privacy dashboard extension that implements privacy scoring computations to enhance transparency toward collateral information collection. Furthermore, we discuss alternative solutions highlighting other countermeasures such as notification and access control mechanisms, cryptographic solutions and application auditing. To the best of our knowledge this is the first work that provides a detailed multi-faceted study of this problem and that analyses the threat of user profiling by application providers. <s> BIB013
Raynes-Goldie studies the privacy risks on OSNs and the associated concerns through an ethnographic study of FB users (N ≈ 20) in Toronto [Raynes-Goldie 2010]. The study tackles (among other things) interdependent privacy risks related to the fact that users can pass forward to others the content they have access to (e.g., photos). They mention, for instance, the case where a user blocked by an ex-lover asks a common friend to access and pass to the user the photos shared by their ex. Although the threat is real, it is very hard-if not impossible-to mitigate. In addition, the fact that the process is not automated reduces the extent of the threat. Akcora et al. identify and investigate the case where the privacy policies and photo-tagging actions of users of OSNs put the privacy of their friends at risk BIB004 ]. Indeed, when users set the visibility of the content they post to "friends only," the content could actually be, in certain circumstances, visible to users other than their friends. 23 For instance, on FB, if a user comments on some content posted by one of their friends, the content becomes visible to their own friends, thus propagating beyond what the user who posted it intended. 24 The authors study the risk perception of users, toward the disclosure of photos to friends of friends and strangers, and the underlying reasons and factors. Damen et al. also investigate the loss of control of users on the access to the content they or their friends share BIB005 ]. The authors survey such risks on FB and propose tools for assisting FB users in determining, depending on the actions of other users and the visibility of certain content including pictures. Henne et al. identify and investigate issues related to user (un)awareness about the media (including photos) that features them on OSNs BIB006 ]. To do so, they rely on a survey of N = 414 users. The survey results highlight that 52% of the respondents learned by chance about shared photos that feature them. In some cases, when new content is shared by a stranger, the content cannot be removed, because the featured user is not even aware of this content. Ilia et al. study the same issues, focusing on pictures, and they investigate the tagging habits of individuals BIB008 . The authors explore this issue by collecting photos through a user study of N = 128 FB users. The results show that 92% of users have access to photos that depict strangers. They also show that individuals are not always tagged, as more than 87% of pictures contain only one tag, and 75% contain at least two distinguishable faces. Such et al. focus on the same issues and show that the vast majority of users experience such multi-party privacy conflicts (99.3%) , both as the users sharing the photos (uploader) and as those featured in the photos (co-owner). They also find that most of these conflicts are related to media captured during social events (e.g., Christmas) and happened on FB. Concerns. Besmer and Richter Lipford study user privacy concerns related to the sharing and tagging of photos on OSNs BIB002 . Using three focus groups, with a total of N = 14 individuals, they identify the different actors who are perceived as adversaries (i.e., potential viewers) by individuals. Their results show that the privacy concerns are related mostly to individuals from personal social circles such as family members, friends, and employers, but not from strangers or from the service provider and its associates-a finding common to other studies, e.g., BIB001 ; Raynes-Goldie [2010] . They also show that privacy concerns are caused by the fact that the photos portray non-normal behaviors, such as illegal activities or unflattering behaviors. Wang et al. study general users regrets regarding post on OSNs, including in interdependent privacy situations BIB003 ]. The study is based on data collected through surveys on MTurk (N = 813) and interviews (N = 19) from Facebook users recruited on Craigslist. The authors reported that three interviewees (out of 19) showed regrets about sharing group photos (e.g., at parties) that impacted others negatively, showing them with embarrassing behaviors (e.g., underage drinking), or with an unflattering look. Choi et al. study user perception regarding the disclosure, by others, of embarrassing contents such as photos on OSNs BIB009  . The authors rely on the CPM theory (see Section 3.4). In particular, building on an abundant literature for the offline case (i.e., in the real world, by opposition to the Internet), they focus on the situations where some content is disclosed on an OSN to tease a target individual. To test their model, the authors conducted a user study with N = 109 FB users from a student population of a university in south-east Asia; and they relied on hypothetical embarrassing disclosures. The authors investigate which factors influence the target individuals' perception of the privacy invasion and show that, in the general case, tagging the content with the identity of the target increases the perceived invasion. They also study how target individuals react to such invasions. Chen et al. focus on privacy concerns when content is disclosed by peers; more specifically, they investigate how individuals would make decisions if they could control-to some extent-which content about themselves others could disclose on OSNs BIB010 . They put an emphasis on photos, and more specifically on photo tagging. They introduce the concept of information privacy concern about peer disclosure (IPCPD) and rely on CPM and impression management to analyze such privacy concerns. They focus on two aspects of privacy management theory: the "what" (i.e., the content) and the "for whom" (i.e., the audience). And they capture these aspects through the discrepancy between the image projected by the content and the online identity of the individual, and the social network overlap (between the individual featured in the content and the individual who shares it). To test their model, they conduct a laboratory experience with N = 139 undergraduate students, by using short scenarios mixing high and low values for the three parameters of the model (i.e., discrepancy, social network overlap, and decisional control), where students had to evaluate their privacy concerns and their control variables. The results show that privacy concerns depend on the type of content to be disclosed and on the audience who has access to the content. More importantly, the privacy concerns change in function of the degree of decision control that users have. Ozdemir et al. also study the privacy concerns of individuals when content is disclosed by peers (which they call disclosure in peer contexts) BIB012 ]. The authors rely on the "antecedents, privacy concerns, outcomes" (APCO) model to evaluate these concerns, and extend it with the constructs of risk, trust, and benefit. They define several hypotheses to test their model, e.g., higher privacy awareness is associated with higher information privacy concern, higher risk is associated with lower perceptions of trust, and more perceived benefit increase the information disclosed online. Then they evaluate the hypotheses with an online survey questionnaire N = 314 U.S. FB users. Their results support their hypothesis and highlight the importance of privacy experiences and the privacy awareness construct in individuals' privacy concerns. They also show that information disclosure significantly depends on the benefits obtained by sharing content, the trust in other peers and the privacy concerns of individuals. Symeonidis et al. study user concerns regarding the interdependent-privacy risks of third-party social network apps (identified by Wang et al. and investigated by Biczók and Chia) that they refer to as collateral damage BIB011  . They rely on an online survey with N = 114 FB users. They find that 66% of the participants are at least very concerned about the fact that, by default, FB enables apps to access information about a user's friends; and 77% are at least very concerned about not being notified when such situations occur. Furthermore, they find that users are also concerned about the privacy risks they expose their friends to, thus showing some form of altruism regarding privacy, as considered in other works (e.g., BIB007 ). We discuss these works in Section 5.1.1. In a follow-up work, Symeonidis et al. revisit their initial investigation in the light of the Cambridge Analytica scandal and complement it with a legal analysis based on the General Data Protection Regulation of the European Union (EU GDPR) BIB013 ]. Jia and Xu study collective privacy concerns in OSNs, which rely on the CPM theory [Jia and Xu 2016b] (see Section 3.4). The authors evaluate these concerns at diffusion, access and control dimensions. To do so, they study the current literature about privacy concerns and they collected data via an online survey, from the U.S. population of undergraduate students (N = 427). Their results show that individuals are concerned with these three dimensions of privacy and more than 50% of participants are frequent users of OSNs, hence the importance of these new privacy concerns. Chutikulrungsee and Burmeiste study Facebook users privacy concerns (including conflicts) for photos sharing in OSNs [Chutikulrungsee and Burmeiste 2017]. The authors collected data about user behaviors regarding shared contents (i.e., photos, tags, comments) deletion requests, with an online survey with N = 460 participants recruited on SurveyMonkey. The results show that more than one-fourth of the participants requested (at least once) another user to remove a shared picture in the past.