Despite its practical impact, closed-box fuzzing on web applications remains understudied. This paper investigates two fundamental limitations of closed-box web fuzzing: (1) limited input space exploration due to the lack of a feedback mechanism, and (2) ineffective exploitation strategies caused by the shallow vulnerability identification. We propose Zelda, a novel closed-box web fuzzer designed to address these limitations. Specifically, we infer feedback signals from web responses in a closed-box testing environment, thereby deriving a feedback mechanism to guide the fuzzing process. We then coordinate two distinct input generation strategies for path exploration and exploitation, based on the exploration stage, which facilitates both in-page code coverage and vulnerability identification. Our evaluation across 15 real-world applications and nine benchmark sets demonstrates that Zelda's feedback mechanism and strategies are effective in practical web vulnerability discovery. Zelda uncovered 182 vulnerabilities, outperforming six state-of-the-art web fuzzers. In the wild, Zelda further discovered previously unreported vulnerabilities that received 29 CVE assignments.

Phishing attacks continue to be a major threat to internet users, causing data breaches, financial losses, and identity theft. This study provides an in-depth analysis of the lifespan and evolution of phishing websites, focusing on their survival strategies and evasion techniques. We analyze 286,237 unique phishing URLs over five months using a custom web crawler based on Puppeteer and Chromium. Our crawler runs on a 30-minute cycle, systematically checking the operational status of phishing websites by collecting their HTTP status codes, screenshots, HTML, and HTTP data. Temporal and survival analyses, along with statistical tests, are used to examine phishing website lifecycles, evolution, and evasion tactics. Our findings show that the average lifespan of phishing websites is 54 hours (2.25 days) with a median of 5.46 hours, indicating rapid takedown of many sites while a subset remains active longer. Interestingly, logistic-themed phishing websites (e.g., USPS) operate within a compressed timeframe (1.76 hours) compared to other brands (e.g., Facebook). We further analyze detection effectiveness using Google Safe Browsing (GSB). We find that GSB detects only 18.4% of phishing websites, taking an average of 4.5 days. Notably, 83.93% of phishing sites are already taken down before GSB detection, meaning GSB requires more prompt detection. Moreover, 16.07% of phishing sites persist beyond this point, surviving for an additional 7.2 days on average, resulting in an average total lifespan of approximately 12 days. We reveal that DNS resolution error is the main cause (67%) of phishing website takedowns. Finally, we uncover that phishing sites with extensive visual changes (more than 100 times) exhibit a median lifespan of 17 days, compared to 1.93 hours for those with minimal modifications. These results highlight the dynamic nature of phishing attacks, the challenges in detection and prevention, and the need for more rapid and comprehensive countermeasures against evolving phishing tactics.

Phishing attacks pose a significant threat to Internet users. Understanding the security posture of phishing infrastructure is crucial for developing effective defense strategies, as it helps identify potential weaknesses that attackers might exploit. Despite extensive research, there may still be a gap in fully understanding these security weaknesses. To address this important issue, this paper presents a longitudinal study of security configurations and vulnerabilities in phishing websites and associated kits. We focus on two main areas: (1) analyzing the security configurations of phishing websites and servers, particularly HTTP headers and application-level security, and (2) examining the prevalence and types of vulnerabilities in phishing kits. We analyze data from 906,731 distinct phishing websites collected over 2.5 years, covering HTML headers, client-side resources, and phishing kits. Our findings suggest that phishing websites often employ weak security configurations, with 88.8% of the 13,344 collected phishing kits containing at least one potential vulnerability, and 12.5% containing backdoor vulnerabilities. These vulnerabilities present an opportunity for defenders to shift from passive defense to active disruption of phishing operations. Our research proposes a new approach to leverage weaknesses in phishing infrastructure, allowing defenders to take proactive actions to disable phishing sites earlier and reduce their effectiveness.

Transport Layer Security (TLS) has become the norm for secure communication over the Internet. In August 2018, TLS 1.3, the latest version of TLS, was approved, providing improved security and performance of the previous TLS version. In this paper, we take a closer look at TLS 1.3 deployments in practice regarding adoption rate, security, performance, and implementation by applying temporal, spatial, and platform-based approaches on 687M connections.

In this paper, we present a new ad budget draining attack. By repeatedly pulling ads from targeted advertisers using crafted browsing profiles, we are able to reduce the chance of showing their ads to real-human visitors and trash the ad budget. From the advertiser profiles collected by an automated crawler, we infer advertising strategies, train satisfying browsing profiles and launch large-scale attacks. We evaluate our methods on 291 public advertisers selected from Alexa Top 500, where we successfully reveal the targeting strategies used by 87% of the advertisers we considered. We also executed a series of attacks against a controlled advertiser and 3 real-world advertisers within the ethical and legal boundary. The results show that we are able to fetch 40,958 ads and drain up to $155.89 from the targeted advertisers within an hour.

Web-based malware equipped with stealthy cloaking and obfuscation techniques is becoming more sophisticated nowadays. In this paper, we propose J-FORCE, a crash-free forced JavaScript execution engine to systematically explore possible execution paths and reveal malicious behaviors in such malware. In particular, J-FORCE records branch outcomes and mutates them for further explorations. J-FORCE inspects function parameter values that may reveal malicious intentions and expose suspicious DOM injections. We addressed a number of technical challenges encountered. For instance, we keep track of missing objects and DOM elements, and create them on demand. To verify the efficacy of our techniques, we apply J-FORCE to detect Exploit Kit (EK) attacks and malicious Chrome extensions. We observe that J-FORCE is more effective compared to the existing tools.