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1. Click This, Not That: Extending Web Authentication with Deception

   https://doi.org/10.1145/3433210.3453088  

   Barron, Timothy; So, Johnny; Nikiforakis, Nick (May 2021, Proceedings of the 2021 ACM Asia Conference on Computer and Communications Security (ASIACCS))

   null (Ed.)

   With phishing attacks, password breaches, and brute-force login attacks presenting constant threats, it is clear that passwords alone are inadequate for protecting the web applications entrusted with our personal data. Instead, web applications should practice defense in depth and give users multiple ways to secure their accounts. In this paper we propose login rituals, which define actions that a user must take to authenticate, and web tripwires, which define actions that a user must not take to remain authenticated. These actions outline expected behavior of users familiar with their individual setups on applications they use often. We show how we can detect and prevent intrusions from web attackers lacking this familiarity with their victim's behavior. We design a modular and application-agnostic system that incorporates these two mechanisms, allowing us to add an additional layer of deception-based security to existing web applications without modifying the applications themselves. Next to testing our system and evaluating its performance when applied to five popular open-source web applications, we demonstrate the promising nature of these mechanisms through a user study. Specifically, we evaluate the detection rate of tripwires against simulated attackers, 88% of whom clicked on at least one tripwire. We also observe web users' creation of personalized login rituals and evaluate the practicality and memorability of these rituals over time. Out of 39 user-created rituals, all of them are unique and 79% of users were able to reproduce their rituals even a week after creation. 

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2. DALock: Password Distribution-Aware Throttling

   Blocki, Jeremiah; Zhang, Wuwei. (January 2022, Proceedings on Privacy Enhancing Technologies)

   Large-scale online password guessing attacks are widespread and pose a persistant privacy and security threat to users. The common method for mitigating the risk of online cracking is to lock out the user after a fixed number ($$K$$) of consecutive incorrect login attempts. Selecting the value of $$K$$ induces a classic security-usability trade-off. When $$K$$ is too large, a hacker can (quickly) break into a significant fraction of user accounts, but when $$K$$ is too low, we will start to annoy honest users by locking them out after a few mistakes. Motivated by the observation that honest user mistakes typically look quite different from an online attacker's password guesses, we introduce $$\DALock$$, a {\em distribution-aware} password lockout mechanism to reduce user annoyance while minimizing user risk. As the name suggests, $$\DALock$$ is designed to be aware of the frequency and popularity of the password used for login attacks. At the same time, standard throttling mechanisms (e.g., $$K$$-strikes) are oblivious to the password distribution. In particular, $$\DALock$$ maintains an extra ``hit count" in addition to ``strike count" for each user, which is based on (estimates of) the cumulative probability of {\em all} login attempts for that particular account. We empirically evaluate $$\DALock$$ with an extensive battery of simulations using real-world password datasets. In comparison with the traditional $$K$$-strikes mechanism, {our simulations indicate that} $$\DALock$$ offers a superior {simulated} security/usability trade-off. For example, in one of our simulations, we are able to reduce the success rate of an attacker to $$0.05\%$ (compared to $$1\%$$ for the $$3$$-strikes mechanism) whilst simultaneously reducing the unwanted lockout rate for accounts that are not under attack to just $$0.08\%$$ (compared to $$4\%$$ for the $$3$$-strikes mechanism). 

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3. “In Eighty Percent of the Cases, I Select the Password for Them”: Security and Privacy Challenges, Advice, and Opportunities at Cybercafes in Kenya

   Collins Munyendo and Yasemin Acar and and Adam J. Aviv (May 2023, 2023 IEEE Symposium on Security and Privacy)

   Cybercafes remain a popular way to access the Internet in the developing world as many users still lack access to personal computers. Coupled with the recent digitization of government services, e.g. in Kenya, many users have turned to cybercafes to access essential services. Many of these users may have never used a computer, and face significant security and privacy issues at cybercafes. Yet, these challenges as well as the advice offered remain largely unexplored. We investigate these challenges along with the security advice and support provided by the operators at cybercafes in Kenya through n = 36 semi-structured interviews (n = 14 with cybercafe managers and n = 22 with customers). We find that cybercafes serve a crucial role in Kenya by enabling access to printing and government services. However, most customers face challenges with computer usage as well as security and usability challenges with account creation and password management. As a workaround, customers often rely on the support and advice of cybercafe managers who mostly direct them to use passwords that are memorable, e.g. simply using their national ID numbers or names. Some managers directly manage passwords for their customers, with one even using the same password for all their customers. These results suggest the need for more awareness about phone-based password managers, as well as a need for computer training and security awareness among these users. There is also a need to explore security and privacy advice beyond Western peripheries to support broader populations 

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4. A Measurement Study of Authentication Rate-Limiting Mechanisms of Modern Websites

   https://doi.org/10.1145/3274694.3274714  

   Lu, Bo; Zhang, Xiaokuan; Ling, Ziman; Zhang, Yinqian; Lin, Zhiqiang (January 2018, Proceedings of the 34th Annual Computer Security Applications Conference)

   Text passwords remain a primary means for user authentication on modern computer systems. However, recent studies have shown the promises of guessing user passwords efficiently with auxiliary information of the targeted accounts, such as the users' personal information, previously used passwords, or those used in other systems. Authentication rate-limiting mechanisms, such as account lockout and login throttling, are common methods to defeat online password cracking attacks. But to date, no published studies have investigated how authentication rate-limiting is implemented by popular websites. In this paper, we present a measurement study of such countermeasures against online password cracking. Towards this end, we propose a black-box approach to modeling and validating the websites' implementation of the rate-limiting mechanisms. We applied the tool to examine all 182 websites that we were able to analyze in the Alexa Top 500 websites in the United States. The results are rather surprising: 131 websites (72%) allow frequent, unsuccessful login attempts without account lockout or login throttling (though some of these websites force the adversary to lower the login frequency or constantly change his IP addresses to circumvent the rate-limiting enforcement). The remaining 51 websites are not absolutely secure either: 28 websites may block a legitimate user with correct passwords when the account is locked out, effectively enabling authentication denial-of-service attacks. 

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5. Secure Account Recovery for a Privacy-Preserving Web Service

   Little, Ryan; Qin, Lucy; Varia, Mayank (August 2024, USENIX Association)

   If a web service is so secure that it does not even know---and does not want to know---the identity and contact info of its users, can it still offer account recovery if a user forgets their password? This paper is the culmination of the authors' work to design a cryptographic protocol for account recovery for use by a prominent secure matching system: a web-based service that allows survivors of sexual misconduct to become aware of other survivors harmed by the same perpetrator. In such a system, the list of account-holders must be safeguarded, even against the service provider itself. In this work, we design an account recovery system that, on the surface, appears to follow the typical workflow: the user types in their email address, receives an email containing a one-time link, and answers some security questions. Behind the scenes, the defining feature of our recovery system is that the service provider can perform email-based account validation without knowing, or being able to learn, a list of users' email addresses. Our construction uses standardized cryptography for most components, and it has been deployed in production at the secure matching system. As a building block toward our main construction, we design a new cryptographic primitive that may be of independent interest: an oblivious pseudorandom function that can either have a fully-private input or a partially-public input, and that reaches the same output either way. This primitive allows us to perform online rate limiting for account recovery attempts, without imposing a bound on the creation of new accounts. We provide an open-source implementation of this primitive and provide evaluation results showing that the end-to-end interaction time takes 8.4-60.4 ms in fully-private input mode and 3.1-41.2 ms in partially-public input mode. 

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