Understanding the Privacy Implications of Using Context-based Awareness Cues in Social Networks


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Information from the physical world is increasingly being digitalized and shared in social networks. We share our locations, tag photos and add different kinds of informal awareness cues about the physical world to our online communities. In this paper, we investigate the privacy implications of shared context cues in social networking services. We present an experimental mobile application, which allows users to add different descriptions of context information to their Facebook and Twitter status updates. The application was used by 12 persons during a two-week user trial using their own devices and Facebook accounts. The results indicate that user-defined abstractions of context items were often preferred over more accurate indicators due to privacy concerns or discomfort in sharing. We also found out that using shared context from friends in vicinity needs careful design to overcome the extended privacy implications.

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Understanding the Privacy Implications of Using Context-based Awareness Cues in Social Networks

  1. 1. Understanding the Privacy Implications of Using Context-based Awareness Cues in Social Networks Ville Antila Jussi Polet Context-Awareness and Service Interaction Context-Awareness and Service Interaction VTT Technical Research Centre of Finland VTT Technical Research Centre of Finland Oulu, Finland Oulu, Finland ville.antila@vtt.fi jussi.polet@vtt.fiAbstract — Information from the physical world is increasingly the user, the currently active applications in the mobilebeing digitalized and shared in social networks. We share our device, information about the current device, informationlocations, tag photos and add different kinds of informal about the friends around, the current location as well asawareness cues about the physical world to our online information about the surroundings. We deliberately selectedcommunities. In this paper, we investigate the privacy a wide variety of context types (even some moreimplications of shared context cues in social networking unconventional ones) to get better understanding over whichservices. We present an experimental mobile application, types of information are considered useful and which arewhich allows users to add different descriptions of context more privacy sensitive than others. Through a two-week userinformation to their Facebook and Twitter status updates. The trial we explored the usage and privacy implications ofapplication was used by 12 persons during a two-week user different abstraction levels when publicly sharing contextualtrial using their own devices and Facebook accounts. Theresults indicate that user-defined abstractions of context items information. The goal was to shed light into the practical usewere often preferred over more accurate indicators due to of context information in informal information sharing andprivacy concerns or discomfort in sharing. We also found out the implications that these practices have in designingthat using shared context from friends in vicinity needs careful context-aware applications, especially regarding thedesign to overcome the extended privacy implications. perceived privacy effects. Keywords - Awareness Cues; Context-awareness; Mobile II. RELATED WORKApplications; Privacy; Sensing; Social Networks; Through the analysis of contextual information derived from mobile device usage patterns it is possible to infer a lot I. INTRODUCTION of potentially privacy-sensitive information. Eagle and Pentland demonstrate the ability to use mobile devices to Social networks are increasingly used to share digital recognize social patterns, infer relationships, identify sociallyartefacts, which are often “tagged” with contextual significant locations, and model organizational rhythms [4].information from the situation or event, mirroring its These life patterns can be used as input for creating narrativephysical counterpart. Photos can be tagged with GPS events [17]. In the work of Miluzzo et al. they propose acoordinates, or presence information can be shared by an system, which is capable of sensing various activitiesinstant messaging application. Furthermore, location check- (location, physical activity, social and physical surroundings)ins, adding sports activities and giving informal awareness and share this information on various social networkingcues in status updates are increasingly used functionalities in platforms [12, 13]. Moreover, the use of mobile devices toSNSs (Social Networking Services), such as the Facebook. create context-aware content to social networking servicesIn many cases the shared information is tailored to a specific has grown recently. Services such as Foursquare, andcase, containing detailed information like GPS coordinates Facebook Places can be used to check-in to venues usingwith textual descriptions, which can render the information mobile devices equipped with GPS-chips. In [21] contexttoo specific or too ambiguous to fit different use cases. Often information, such as location, proximity of friends andthe level of information disclosure can be also hard to motion, is used to create suggestion and validation of check-manage for the user. We claim that in order to ensure the ins into these kinds of applications. Furthermore, location-privacy and user control there should be means for based formation of social networks has been researchedabstracting this information regarding the specific needs and recently [10]. As the social computing is getting moredesires of the user. mobile and pervasive there has been an increase in interest of In this paper, we investigate the practices of abstracting exploring the social-side of context-awareness [5]. Incontextual information for public (or semi-public) sharing. addition to mere location or physical activity of the user, theTo facilitate this, we have developed an experimental mobile systems could benefit from the knowledge of the socialapplication, which allows users to add different types of surroundings. For example, there has been research tocontextual information to their Facebook status updates in a explore the social use of ubiquitous computing in urban areasformat of a story. The types of contextual information [7]. In this paper, we suggest mechanisms to gather contextexplored in this study include the current physical activity of from the surroundings to enhance both availability and
  2. 2. relevance of context information (e.g. querying the devices Our hypothesis is that in many cases, rather than using exactaround). In addition, we investigate the extended privacy parameters provided by context recognition modules forimplications of such sharing mechanisms from the user’s describing the situation, people would like to add semanticpoint-of-view and point out design challenges based on the meaning by using more abstract notions. As Benford et al.findings. argue: “[in this context,] declaring one’s position is perhaps as much about deixis (pointing at and referencing features of III. PRIVACY IMPLICATIONS OF CONTEXT-AWARENESS IN the environment) as it is about telling someone exactly where SOCIAL APPLICATIONS you are” [2]. In addition Tang et al. argue that social-driven The perceived privacy implications of shared presence location sharing favours semantic labels and informationinformation are largely related to the information type as blurring, but also use location sharing as a way to boost self-well as the intended audience, but people are also willing to presentation [19].stretch the boundaries of privacy in exchange for useful In this work, we explore not only the differentservices [9]. Privacy is a dynamic and continuously abstractions of location information, but also othernegotiated process [16]; in practice people tend to commonly available and used context information types. Weappropriate the usage of a service for their own needs [1]. selected six basic information types that the users could useFrom the technical point-of-view there are two distinct to describe their context. The selected context types areapproaches. First, there has been research on developing activity, applications, device, friends, location andframeworks to help the development of privacy-aware surroundings. These context types are described more in theparticipatory sensing applications. For example in [3] the next sections. Furthermore, we were interested in theprivacy implications of sharing the sensory data of one’s perceived privacy of different levels of abstraction ofmobile device are discussed and a framework is presented. contextual information.Similarly, in [8] a privacy-aware framework is proposed, The narrative status update message is generated fromwhich enables the sharing of contextual data between users the freeform user-inputted status message and the contextand central servers while at the same time maintaining the information gathered by the mobile application and selectedsecurity and privacy of each user. Furthermore, there has by the user. The rule for generating the message is asbeen some recent research on enabling the knowledge of the follows:situation and its privacy implications to automatize certainfunctionalities. For example, in [6] contextual data is used to “[User-defined message]determine the mobile device locking timeout and unlocking Sent from [Location] using [Device] with [Friends]method dynamically, depending on the perceived safety of nearby, while [Activity] and [Applicationsthe current context (home, office etc.). On the other hand, in many application cases the notion Activity] in [Surroundings].”of context itself is very dynamic and ever-changing. Manciniet al. argue that context is not objectively defined by settings, As an example, a status update message generated withactions or actors themselves but by the meaning that they the previous rule could be (not all context fields selected):acquire at any given time from the subjective perspective[11]. Furthermore the privacy preferences themselves also “Thinking of mesh-networks!change in time and are dynamic in different situations.Awareness of consequences of contextual information Sent from Lugano, Switzerland with 2 Facebook friendssharing is said to be important factor for the users to get a nearby, while walking and using Maps.”better grasp on how their actions affect the level of V. PROTOTYPE APPLICATIONinformation disclosure [18, 20]. One of our leading designgoals in this work has been to explore the practical usage of The prototype application consists of a mobile client anddifferent levels of abstractions by giving the user full control a server-side application, which is integrated with Facebookover the level of information they share. and Twitter. The overall prototype architecture is depicted in the Figure 1. IV. CONTEXT-BASED AWARENESS CUES The mobile application gathers context data from the Oulasvirta et al. have studied how sharing context device itself, available sensors and by using Bluetooth toinformation could create awareness about the user’s situation collect data from nearby devices. The application presentsand thus enhance communication and collaboration [14]. the sensed context information to the user along withThey also discuss the different design requirements for proposals for other semantic abstractions, which have beenrepresenting context-based awareness cues [15]. used to describe similar contexts earlier. User can also define To explore the usage of shared context cues, we a new context element which will be then coupled with thedeveloped an application which allows people to include raw context data gathered from that situation (enabling thecontextual information to their status updates they send to application to suggest it later on). After selecting the contextFacebook. In addition to the selection of different context items and their abstractions, the status update is sent to thetypes, the user can also decide the desired abstraction level server. The server application stores the received context(e.g. coordinates, address or semantic label such as “office”). data into a semantic model (including the raw data from the sensors and the associated abstraction) and creates a context-
  3. 3. enhanced status update, which is used to create a new status A. Context Recognitionupdate in Facebook (Figure 2). The context recognition is based on different “sensors” on the mobile device, such as the accelerometer, ambient light detector and GPS data, the open applications on the Social Media mobile device, the device system information, the nearby Bluetooth devices and the WLAN access points. Based on ContextCapture this data, context descriptions and suggestions are shown to Server the user. For example, based on the ambient light detector data, information about the current lighting is shown to user, such as “Dark lighting” or based on the GPS data, the Web current street address, GPS coordinates and current temperature and weather descriptions are shown. In the list below we describe all the context information items Network supported by the application: User connection with (3G/WLAN) Mobile Phone Other user • Activity – Based on the accelerometer data, a decision is with mobile made whether the user is running, walking or still by phone using movement detection algorithms. This is then Bluetooth shown to the user as a description of the current physical connection activity abstraction. • Applications – Based on the data gathered from the mobile device, the currently open applications are shown to the user as a description of the current virtual activity abstraction. • Device – Some of the data gathered about the mobile device itself, such as the device type, is shown to the user. • Friends – Based on the Bluetooth device and service scan data, the current nearby Bluetooth devices and ContextCapture friends are shown to the user as the current social context. The current ContextCapture friends’ detection is based on the Facebook friends and ContextCapture use, i.e. if the users are friends in the Facebook and both are using ContextCapture and are nearby, they are shown in the current social context abstractions. • Location – Based on the GPS, network and WLAN scan data, the current street address, GPS coordinates, network cell ID and nearby WLAN access points are shown as the possible current location abstractions. • Surroundings – Based on the ambient light detector and Figure 1. Left-Up: The prototype architecture. Right and GPS data, the current ambient lighting and the Bottom: The ContextCapture mobile application UI. temperature and weather (which are downloaded based on the GPS coordinates) are shown as the current physical surroundings abstractions. B. Protocol for Exchanging Collective Context The client-to-client communication is done over a Bluetooth connection, using a specified communication protocol. The mobile client notices whether there are other devices nearby offering the specified service. If so, the devices exchange MD5-hashed IDs, which are coupled with the Facebook accounts. If the mobile client is lacking some context information, for example the GPS coordinates; it will request that information from the nearby friends, which will reply with the data, should they possess it. The syntax for the exchange protocol is as follows:Figure 2. Example of using context-based awareness cues in a status update shown on Facebook
  4. 4. CCRAControlProtocol:<role_name>:<BT_name>: VI. USER STUDY <command>:<parameters> To evaluate the ContextCapture application and to find answers to our research questions, we arranged a trial, where For example, the mobile client requesting for weather 12 participants used ContextCapture for two weeks withdata from a nearby ContextCapture friend takes the client their own mobile phones in their everyday lives. This sectionrole and sends a request as follows: introduces the user study and the results from the trial. A. User study design CCRAControlProtocol:Client:ClientBluetooth Name:WTHR:Request The aim of the evaluation was to study how people would use context information in their status updates and what kind of abstraction levels would be suitable for And the service running on the specified device replies: presenting the context information regarding the perceived privacy effects. To discover these matters, two distinct CCRAControlProtocol:Server:ServerBluetooth research questions were set: Name:WTHR:-3 degrees Celsius,Sunny 1. How do users perceive privacy implications of The ContextCapture Facebook application is located at shared context cues in social settings (such as statusthe server and relays the incoming status update messages updates)?from the mobile client to the Facebook. The client-to-server 2. How do users perceive the privacy implications ofcommunication is based on normal HTTP GET and POST collaborative context gathered from theoperations, where the data sent is JSON formatted. The two surroundings (such as identifying friends in theirmain communication sequences between the mobile client status updates)?and the server are the login and status update. In the login sequence, the mobile client sends the login As we wanted to ensure that all significant data would bekey, which the user has got from the ContextCapture collected, various data collection methods were used. In theFacebook application and the MD5-hashed IMSI string. This beginning of the trial we had an initial web questionnaire,way, the user’s Facebook account and the user’s mobile which included questions about the Facebook usage anddevice are coupled together at the server by using the expectations towards the ContextCapture application. DuringFacebook user ID, ContextCapture login key and the MD5- the trial, participants could report about their experienceshashed IMSI string. with the application through a web-based diary In the status update sequence, the mobile client sends a questionnaire. The diary inquired, which of the context typesJSON formatted data package containing all the context data had been most useful to the participants and whether theyand the user-given abstractions to server. The server then had got any comments and feedback from their Facebookparses the message and creates a story-like status update friends related to the contextual status updates. It alsostring, which is sent as a wall post to Facebook. Depending included questions about the experiences related to privacy.on the success, the server sends back a reply, which also The participants could also give general free-formattedcontains the current ContextCapture friends so that the feedback about the study through the diary questionnaire. Atmobile client can update the friends list if there have been the end of the trial all participants were interviewed forchanges. getting more in-depth information about the user experience. Interviews also included a background information sheet,C. Used Technologies which was given on paper. It contained demographical and The mobile application was implemented for Symbian closed scale questions, which were easier to ask in writtenand Android devices. Qt was used in the Symbian form.application and the persistent storage for context data wasimplemented with the Qt APIs for SQLite. The server-side B. Participantsimplementation was developed using J2EE web framework. The first criterion for the trial participants was the factThe contextual data is saved using RDF format with Jena that they had to be active Facebook users. Some of theSemantic Web Toolkit and persisted in a PostgreSQL participants had to be connected through Facebook, as wedatabase. The context information was chosen to be persisted wanted to have groups of people, who could see each other’sin the server-side for two reasons, one reason was that we status updates and be able to use friends related contextwanted to control the user study results, and the other reason information via “Facebook friends nearby” –functionality. Inwas to use the gathered context information as the basis of addition, the participants had to have suitable mobile phonescollective intelligence, enabling recommendation and supported by the application. Due to this, we decided toadaptive filtering content based on the context in later stages invite only VTT 1 and NRC (Nokia Research Centre) 2of the research. The SNS integration was implemented using employees to the user study.the Facebook and Twitter APIs, which enablesfunctionalities such as the user authentication and status 1 http://www.vtt.fi/?lang=enupdating. 2 http://research.nokia.com/
  5. 5. Total of 12 users participated in the trial, six male and six Sharing friend’s location was also one thing, whichfemale. The age of the participants was between 30-46 years, invoked thoughts. In many participants’ opinion sharing this37.25 years on average. Participants used ContextCapture kind of information without permission is not acceptable. Sowith their own mobile devices and personal Facebook there should be some way for asking a permission to shareaccounts during the trial. All participants were experienced context data including other users. Friends’ names were alsoFacebook users as 25% of them had used the service 1-2 often viewed as private information and participantsyears and the rest for over two years. Figure 3 shows how preferred to use more abstract words, like “group ofoften the participants were used to send status updates before friends”, instead of giving the exact names.the study. One of the key findings was the fact that participants were clearly interested in context data and in using a context- aware application. Context information was seen as highly interesting, but the participants hoped that they could have had even more control in the level of abstraction. In addition, more abstract names like “home”, “work”, “kindergarten” were seen as more useful and secure in many situations than the exact street addresses. There were interest towards getting more specific location information, bare street addresses were seen as not useful, but the application should recognize the place, which is located in the address, like a movie theatre or a shop. E. Implications for design of context-aware social Figure 3. Frequency of sending status updates (generally and applications via mobile phone). Based on the findings we can summarize the implications for the design of context-aware social applications,C. Trial setup especially when dealing with privacy sensitive information, First we sent email instructions to the participants on how as following:to download and install the application. The email included ashort description of the study and its purpose, a short manual, 1. With applications dealing with privacy sensitivethe link and instructions on how to install the application and information, the information disclosure and privacya link to the initial web questionnaire. The users were should be fully controlled by the userrequested to fill in the initial questionnaire after they had 2. By giving the freedom for users to control the disclosuresuccessfully completed the installation of the application. and abstraction level of contextual information, weThis indicated that they had started the trial. argue that it creates: The participants used the application for approximatelytwo weeks. During that time, they could tell their • Meaningfulness and motivation for the users,experiences through the web diary. We asked them to fill in • And in the same time allows the system tothe diary at least five times and preferably in separate days. gather a set of user-defined context labels withTotal of 26 diary entries were made during the trial. At the different abstraction levels (which can beend of the trial, we interviewed all the participants; nine of associated with the gathered low-level sensorthem with face-to-face interviews and three of them via data).telephone interviews. Interviews were semi-structured,including questions dealing with users’ expectations, The lessons learned from developing the application andattitudes, privacy and the most pleasing and unpleasing running the user study include that it is clearly important toexperiences related to usage. The interviews lasted design the application to give full control of the level ofapproximately 30 minutes each. information disclosure to the user, even case-by-caseD. Findings manner. We found out that privacy is indeed a dynamic and continuously negotiated process in which a rigorous set of The participants were clearly aware of their privacy and prior rules can render the application useless. When put in anhad thought it while using the application. For example, the actual situation, people often appropriate the sharedparticipants did not use the addresses of their homes or information level according to the needs of the momentkindergarten their children were, although the audience rather than using a non-changing privacy policy.consisted of Facebook friends known by the participants. Itseemed that the accurate location of these places was too VII. DISCUSSION AND CONCLUSIONSsensitive to be shared. In addition, many of the participants In this paper, we explored the usage of different typesstated that the semantic meaning of the place is enough. For and abstractions of context information in informalexample, saying that “I’m at home” is adequate enough for information sharing and the practical usage of thesethe people the message is meant for, i.e. my friends know abstractions to maintain certain-level of privacy. Wewhere I live. approached this challenge by developing an experimental
  6. 6. application that allows users to add different context [6] Gupta, A., Miettinen, M. & Asokan, N. Using context-profiling to aidinformation types and abstractions to their Facebook status access control decisions in mobile devices. IEEE International Conference on Pervasive Computing and Communicationsupdates. Workshops (PERCOM Workshops), IEEE, Pp. 310, 2011. In many cases, the participants reported that the usage of [7] Hosio, S., Kukka, H. & Riekki, J. Social Surroundings: Bridging thesemantic labels (abstract) rather than exact terms to describe Virtual and Physical Divide, IEEE MultiMedia Magazine, Vol. 17,the context seemed more appropriate to the situation. No. 2, pp. 26-33, 2010.Moreover the usage of different abstractions was dynamic [8] Kazemi, L. & Shahabi, C. Towards preserving privacy inrather than static. The practical usage of these awareness participatory sensing. 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