Address: Min H. Kao Building, Room 339
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Knoxville, TN 37996-2250

Kyungchan Lim

Degree: PhD
Advisor: Doowon Kim

I’m interested in computer security, especially the areas of data-driven security and web security measurements. I’m currently working in the area of web security, analyzing websites in order to measure security from technical and human-centered perspectives.


Abstract:  Phishing attacks have persistently remained a prevalent and widespread cybersecurity threat for several years. This leads to numerous endeavors aimed at comprehensively understanding the phishing attack ecosystem, with a specific focus on presenting new attack tactics and defense mechanisms against phishing attacks. Unfortunately, little is known about how client-side resources (e.g., JavaScript libraries) are used in phishing websites, compared to those in their corresponding legitimate target brand websites. This understanding can help us gain insights into the construction and techniques of phishing websites and phishing attackers’ behaviors when building phishing websites. In this paper, we gain a deeper understanding of how client-side resources (especially, JavaScript libraries) are used in phishing websites by comparing them with the resources used in the legitimate target websites. For our study, we collect both client-side resources from phishing websites and their corresponding legitimate target brand websites for 25 months: 3.4M phishing websites (1.1M distinct phishing domains). Our study reveals that phishing websites tend to employ more diverse JavaScript libraries than their legitimate websites do. However, these libraries in phishing websites are older (nearly 21.2 months) and distinct in comparison. For example, Socket.IO is uniquely used in phishing websites to send victims’ information to an external server in real time. Furthermore, we find that a considerable portion of them still maintain a basic and simplistic structure (e.g., simply displaying a login form or image), while phishing websites have significantly evolved to bypass anti-phishing measures. Finally, through HTML structure and style similarities, we can identify specific target webpages of legitimate brands that phishing attackers reference and use to mimic for their phishing attacks.
Abstract:  The ever-increasing phishing campaigns around the globe have been one of the main threats to cyber security. In response, the global anti-phishing entity (e. g., APWG) collectively maintains the up-to-date blacklist database (e. g., eCrimeX ) against phishing campaigns, and so do modern browsers (e. g., Google Safe Browsing). However, our finding reveals that such a mutual assistance system has remained a blind spot when detecting geolocation-based phishing campaigns. In this paper, we focus on phishing campaigns against the web portal service with the largest number of users (42 million) in South Korea. We harvest 1,558 phishing URLs from varying resources in the span of a full year, of which only a small fraction (3.8%) have been detected by eCrimeX despite a wide spectrum of active fraudulence cases. We demystify three pervasive types of phishing campaigns in South Korea: i) sophisticated phishing campaigns with varying adversarial tactics such as a proxy configuration, ii) phishing campaigns against a second-hand online market, and iii) phishing campaigns against a non-specific target. Aligned with previous findings, a phishing kit that supports automating the whole phishing campaign is prevalent. Besides, we frequently observe a hit-and-run scam where a phishing campaign is immediately inaccessible right after victimization is complete, each of which is tailored to a single potential victim over a new channel like a messenger. As part of mitigation efforts, we promptly provide regional phishing information to APWG, and immediately lock down a victim’s account to prevent further damages.
Abstract:  Modern Websites rely on various client-side web resources, such as JavaScript libraries, to provide end-users with rich and interactive web experiences. Unfortunately, anecdotal evidence shows that improperly managed client-side resources could open up attack surfaces that adversaries can exploit. However, there is still a lack of a comprehensive understanding of the updating practices among web developers and the potential impact of inaccuracies in Common Vulnerabilities and Exposures (CVE) information on the security of the web ecosystem. In this paper, we conduct a longitudinal (four-year) measurement study of the security practices and implications on client-side resources (e.g., JavaScript libraries and Adobe Flash) across the Web. Specifically, we first collect a large-scale dataset of 157.2M webpages of Alexa Top 1M websites for four years in the wild. Analyzing the dataset, we find an average of 41.2% of websites (in each year of the four years) carry at least one vulnerable client-side resource (e.g., JavaScript or Adobe Flash). We also reveal that vulnerable JavaScript library versions are frequently observed in the wild, suggesting a concerning level of lagging update practice in the wild. On average, we observe 531.2 days with 25,337 websites of the window of vulnerability due to the unpatched client-side resources from the release of security patches. Furthermore, we manually investigate the fidelity of CVE (Common Vulnerabilities and Exposures) reports on client-side resources, leveraging PoC (Proof of Concept) code. We find that 13 CVE reports (out of 27) have incorrect vulnerable version information, which may impact security-related tasks such as security updates.
Abstract:  Password-based authentication is one of the most commonly adopted mechanisms for online security. Choosing strong passwords is crucial for protecting ones' digital identities and assets, as weak passwords can be readily guessable, resulting in a compromise such as unauthorized access. To promote the use of strong passwords on the Web, the National Institute of Standards and Technology (NIST) provides website administrators with password composition policy (PCP) guidelines. We manually inspect popular websites to check if their password policies conform to NIST's PCP guidelines by generating passwords that meet each criterion and testing the 100 popular websites. Our findings reveal that a considerable number of web sites (on average, 53.5 %) do not comply with the guidelines, which could result in password breaches.
Abstract:  Server-side malware is one of the prevalent threats that can affect a large number of clients who visit the compromised server. In this paper, we propose Dazzle-attack, a new advanced server-side attack that is resilient to forensic analysis such as reverse-engineering. Dazzleattack retrieves typical (and non-suspicious) contents from benign and uncompromised websites to avoid detection and mislead the investigation to erroneously associate the attacks with benign websites. Dazzleattack leverages a specialized state-machine that accepts any inputs and produces outputs with respect to the inputs, which substantially enlarges the input-output space and makes reverse-engineering effort significantly difficult. We develop a prototype of Dazzle-attack and conduct empirical evaluation of Dazzle-attack to show that it imposes significant challenges to forensic analysis.