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Expert and Non-Expert Attitudes towards (Secure) Instant Messaging Alexander De Luca, Google; Sauvik Das, Carnegie Mellon University; Martin Ortlieb, Iulia Ion, and Ben Laurie, Google https://www.usenix.org/conference/soups2016/technical-sessions/presentation/deluca This paper is included in the Proceedings of the Twelfth Symposium on Usable Privacy and Security (SOUPS 2016). June 22–24, 2016 • Denver, CO, USA ISBN 978-1-931971-31-7 Open access to the Proceedings of the Twelfth Symposium on Usable Privacy and Security (SOUPS 2016) is sponsored by USENIX. Expert and Non-Expert Attitudes towards (Secure) Instant Messaging Alexander De Luca1, Sauvik Das2, Martin Ortlieb1, Iulia Ion1, Ben Laurie1 1Google; 2Carnegie Mellon University, Pittsburgh, United States {adeluca,mortlieb,iuliaion,benl}@google.com,[email protected] ABSTRACT curity/privacy over traditional mobile IMs have entered the In this paper, we present results from an online survey with app market. However, there are, as yet, few insights about 1,510 participants and an interview study with 31 partici- how and why users do or do not use these messengers. pants on (secure) mobile instant messaging. Our goal was To bridge this gap in the literature, we performed two stud- to uncover how much of a role security and privacy played ies – an online survey with 1,510 participants and a set of in- in people’s decisions to use a mobile instant messenger. In person interviews with 31 participants. For the interviews, the interview study, we recruited a balanced sample of IT- we recruited a balanced sample of people from the general security experts and non-experts, as well as an equal split public and IT security experts. Furthermore, to better rep- of users of mobile instant messengers that are advertised as resent arguments both for and against using secure or pri- being more secure and/or private (e.g., Threema) than tra- vate mobile messengers, we recruited a balanced sample of ditional mobile IMs. Our results suggest that peer influence people who either used or did not use mobile IMs advertised is what primarily drives people to use a particular mobile as secure or private. Our primary goal was to understand IM, even for secure/private IMs, and that security and pri- the reasons why people use mobile IMs in general, as well as vacy play minor roles. whether and how privacy and security influenced people’s 1. INTRODUCTION decisions to use particular mobile IMs. Furthermore, we Due to increasing processing power, modern smartphones also wanted to explore the differences between IT security offer access to manifold services like games, navigation and experts, i.e., people who have the knowledge to make in- even office applications. Despite this multi-faceted function- formed privacy and security decisions, and non-experts and ality, communication is still one of the most important rea- whether they behaved differently in their use of mobile IMs sons why people use smartphones [1, 10] and, as opposed to (e.g., more or less secure). most other smartphone activities, is in constant use through- The results of our study show that privacy and security out the whole day [1]. play a minor role in people’s decisions to use a mobile IM. Mobile instant messaging (MIM), a highly popular form of Security-optimized mobile IMs are not widely adopted and communication, is steadily growing with service providers participants who use them have them for a variety of reasons, such as WhatsApp1 broaching more than 800 million active such as for communicating with a person who is important users.2 With their expansive feature sets, current mobile to them. We also show that while experts are more aware of instant messengers (mobile IMs) have manifold uses, includ- possible risks, they do not necessarily behave more securely ing group chats [22], sharing media files [5], dwelling with than non-experts. friends [13], and even fleeting encounters with strangers [25]. While some of our work extends existing insights, such as As these applications see more use, the privacy and secu- the importance of peer influence on technology adoption, rity problems associated with their use become increasingly into the context of secure/private IMs, our work offers sev- important. More and more apps that promise advanced se- eral novel contributions. For instance, we offer a detailed understanding of why people choose secure IMs and how 1Please note that at the time of the studies reported in this this process differs between lay users and security experts. paper, WhatsApp had not yet introduced end-to-end en- cryption and was encrypted in transit. 2. RELATED WORK 2Announced by founder Jan Koum on Twitter on April 17, Privacy and security in mobile instant messaging has been 2015. approached from different directions. For this work, we are mainly interested in privacy and security attitudes towards common IMs as well as reasons for migrating to more secure IMs or staying with old, potentially insecure messengers. In their work, Patil et al. [14] state that IM users (not exclusively on mobile) have three main desires for privacy: Copyright is held by the author/owner. Permission to make digital or hard privacy from non-contacts, privacy of availability (e.g., their copies of all or part of this work for personal or classroom use is granted status) and privacy of messaging content. For instance, peo- without fee. Symposium on Usable Privacy and Security (SOUPS) 2016, June 22–24, ple are worried that they can be contacted without their ex- 2016, Denver, Colorado. plicit consent, something that most current mobile IMs rely 1 USENIX Association 2016 Symposium on Usable Privacy and Security 147 on (e.g., based on the mobile phone number). In follow-up sengers and how these worked, thus creating an unrealistic work, the authors further found differences in privacy atti- situation. While their study provides many useful insights, tudes towards various categories of contacts [15]. we were more interested in decision making processes and current practices based on the actual, unbiased knowledge Grinter et al. [9] showed that teenagers’ privacy percep- of the users. tions are centered around data protection. They are wor- ried what happens to their messages after they have been received. This includes how a message is stored, whether it 3. MESSENGER SECURITY is ephemeral or long-lived and whether it is further shared This paper is not meant to provide technical details on mes- by the receiver. They often consider possible negative out- senger security and privacy (see Unger et al. [24] for a com- comes of such data leaks and thus want their messages safe. prehensive list of messenger security features). However, it This might explain the success of messaging apps promising is important to mention two kinds of encryption in order zero data retention like Snapchat.3 Technically, these ser- to better understand this work: encryption in transit and vices cannot live up to their promises, creating a potentially end-to-end encryption (e2e). problematic false sense of security [17]. Most modern IMs use encryption in transit. That means the Related to this, proving the identity of the communication messages are sent encrypted from the sender to the server partner is a difficult task. However, identity is an important and the server to the recipient. On the server, they remain factor as users share specific data with specific people but in clear text or in a way that enables at least the service not with others [15]. This has influenced research effort in provider to read the information. In many cases, this fact is using behavioral biometrics to ensure that two communica- used to improve service quality and usability. tion partners are who they claim they are [3]. End-to-end encrypted IMs encrypt the message on the sen- Interestingly, simple features like the “last seen” indicator in der’s phone and it remains in this state until it is decrypted WhatsApp, that are meant to positively support interaction, on the recipient’s phone. No third entity has access to the can be considered problematic by users [2] (despite being information, not even the service provider. End-to-end en- bad predictors for actual attentiveness and causing social cryption comes with some challenges like how to exchange pressure [16]). For instance, users turn such features off to the required keys between the communication entities. For avoid trouble with their partners. further important security attributes and a list of mobile IMs and their security properties, please refer to the EFF It was also shown that for convenience reasons, some messen- secure messaging scorecard.5 gers like WhatsApp and Viber employ practices that might have negative consequences on privacy and security, e.g., The difference between a secure and insecure IM is fuzzy. when they upload whole address books from the smartphone For this work, we used a rather conservative definition: IMs to enable friend finding [21]. Thus, it is not surprising that are secure and/or private if they are actively advertised as many users consider mobile instant messaging to be less se- secure/encrypted/privacy-preserving. This advertising has cure and less privacy-respectful than SMS4 [6]. to be visible on either the website or the store page without scrolling or clicking any links. In most cases, these were even Reasons for using secure mobile IMs or reasons for migrat- part of the title, like for Threema which, at the time of the ing to them have rarely been explored. The most notable study, was titled “Threema. Seriously secure messaging.” work is by Schreiner et al. [20] who created a model based All interview participants who used a “secure IM”, by the on the Push-Pull-Mooring migration framework on privacy above definition, mentioned that they had seen these labels.

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