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Showing posts from March, 2020

On the Effectiveness of Type-based Control Flow Integrity

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Control flow integrity (CFI) has received significant attention in the community to combat control hijacking attacks in the presence of memory corruption vulnerabilities. The challenges in creating a practical CFI has resulted in the development of a new type of CFI based on runtime type checking (RTC). RTC-based CFI has been implemented in a number of recent practical efforts such as GRSecurity Reuse Attack Protector (RAP) and LLVM-CFI. While there has been a number of previous efforts that studied the strengths and limitations of other types of CFI techniques, little has been done to evaluate the RTC-based CFI.

In this work, we study the effectiveness of RTC from the security and practicality aspects. From the security perspective, we observe that type collisions are abundant in sufficiently large code bases but exploiting them to build a functional attack is not straightforward. Then we show how an attacker can successfully bypass RTC techniques using a variant of ROP attacks that…

How Tracking Companies Circumvented Ad Blockers Using WebSockets

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In this study of 100,000 websites, we document how Advertising and Analytics (A&A) companies have used WebSockets to bypass ad blocking, exfiltrate user tracking data, and deliver advertisements. Specifically, our measurements investigate how a long-standing bug in Chrome’s (the world’s most popular browser) chrome.webRequest API prevented blocking extensions from being able to interpose on WebSocket connections.

We conducted large-scale crawls of top publishers before and after this bug was patched in April 2017 to examine which A&A companies were using WebSockets, what information was being transferred, and whether companies altered their behavior after the patch. We find that a small but persistent group of A&A companies use WebSockets, and that several of them engaged in troubling behavior, such as browser fingerprinting, exfiltrating the DOM, and serving advertisements, that would have circumvented blocking due to the Chrome bug.

ACM Internet Measurement Conference (I…

How Tracking Companies Circumvent Ad Blockers Using WebSockets

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In this study of 100,000 websites, we document how Advertising and Analytics (A&A) companies have used WebSockets to bypass ad blocking, exfiltrate user tracking data, and deliver advertisements. Specifically, we leverage a longstanding bug in Chrome (the world’s most popular browser) in the chrome.webRequest API that prevented blocking extensions from being able to interpose on WebSocket connections.

We conducted large-scale crawls of top publishers before and after this bug was patched in April 2017 to examine which A&A companies were using WebSockets, what information was being transferred, and whether companies altered their behavior after the patch. We find that a small but persistent group of A&A companies use WebSockets, and that several of them are engaging in troubling behavior, such as browser fingerprinting, exfiltrating the DOM, and serving advertisements, that would have circumvented blocking due to the Chrome bug.
IEEE S&P Workshop on Technology and Consu…

Large-Scale Analysis of Style Injection by Relative Path Overwrite

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Relative Path Overwrite (RPO) is a recent technique to inject style directives into websites even when no style sink or markup injection vulnerability is present. It exploits differences in how browsers and web servers interpret relative paths (i.e., path confusion) to make a HTML page reference itself as a stylesheet; a simple text injection vulnerability along with browsers’ leniency in parsing CSS resources results in an attacker’s ability to inject style directives that will be interpreted by the browser. Even though style injection may appear less serious a threat than script injection, it has been shown that it enables a range of attacks, including secret exfiltration.

In this paper, we present the first large-scale study of the Web to measure the prevalence and significance of style injection using RPO. Our work shows that around 9 % of the websites in the Alexa Top 10,000 contain at least one vulnerable page, out of which more than one third can be exploited. We analyze in de…

Thou Shalt Not Depend on Me: Analysing the Use of Outdated JavaScript Libraries on the Web

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Web developers routinely rely on third-party JavaScript libraries such as jQuery to enhance the functionality of their sites. However, if not properly maintained, such dependencies can create attack vectors allowing a site to be compromised.

In this paper, we conduct the first comprehensive study of client-side JavaScript library usage and the resulting security implications across the Web. Using data from over 133 k websites, we show that 37% of them include at least one library with a known vulnerability; the time lag behind the newest release of a library is measured in the order of years. In order to better understand why websites use so many vulnerable or outdated libraries, we track causal inclusion relationships and quantify different scenarios. We observe sites including libraries in ad hoc and often transitive ways, which can lead to different versions of the same library being loaded into the same document at the same time. Furthermore, we find that libraries …

"Recommended For You": A First Look at Content Recommendation Networks

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One advertising format that has grown significantly in recent years are known as Content Recommendation Networks (CRNs). CRNs are responsible for the widgets full of links that appear under headlines like “Recommended For You” and “Things You Might Like”. Although CRNs have become quite popular with publishers, users complain about the low-quality of content promoted by CRNs, while regulators in the US and Europe have faulted CRNs for failing to label sponsored links as advertisements.
In this study, we present a first look at five of the largest CRNs, including their footprint on the web, how their recommendations are labeled, and who their advertisers are. Our findings reveal that CRNs still fail to prominently disclose the paid nature of their sponsored content. This suggests that additional intervention is necessary to promote accepted best-practices in the nascent CRN marketplace, and ultimately protect online users.
ACM Internet Measurement Conference (IMC), 2016

[Paper] [Slides]

Identifying Extension-based Ad Injection via Fine-grained Web Content Provenance

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Extensions provide useful additional functionality for web browsers, but are also an increasingly popular vector for attacks. Due to the high degree of privilege extensions can hold, extensions have been abused to inject advertisements into web pages that divert revenue from content publishers and potentially expose users to malware. Users are often unaware of such practices, believing the modifications to the page originate from publishers. Additionally, automated identification of unwanted third-party modifications is fundamentally difficult, as users are the ultimate arbiters of whether content is undesired in the absence of outright malice.
To resolve this dilemma, we present a fine-grained approach to tracking the provenance of web content at the level of individual DOM elements. In conjunction with visual indicators, provenance information can be used to reliably determine the source of content modifications, distinguishing publisher content from content that originates from th…

Tracing Information Flows Between Ad Exchanges Using Retargeted Ads

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Numerous surveys have shown that Web users are concerned about the loss of privacy associated with online tracking. Alarmingly, these surveys also reveal that people are also unaware of the amount of data sharing that occurs between ad exchanges, and thus underestimate the privacy risks associated with online tracking.

In reality, the modern ad ecosystem is fueled by a flow of user data between trackers and ad exchanges. Although recent work has shown that ad exchanges routinely perform cookie matching with other exchanges, these studies are based on brittle heuristics that cannot detect all forms of information sharing, especially under adversarial conditions.

In this study, we develop a methodology that is able to detect client- and server-side flows of information between arbitrary ad exchanges. Our key insight is to leverage retargeted ads as a tool for identifying information flows. Intuitively, our methodology works because it relies on the semantics of how exchanges serve ads,…

UNVEIL: A Large-Scale, Automated Approach to Detecting Ransomware

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Although the concept of ransomware is not new (i.e., such attacks date back at least as far as the 1980s), this type of malware has recently experienced a resurgence in popularity. In fact, in 2014 and 2015, a number of high-profile ransomware attacks were reported, such as the large-scale attack against Sony that prompted the company to delay the release of the film "The Interview". Ransomware typically operates by locking the desktop of the victim to render the system inaccessible to the user, or by encrypting, overwriting, or deleting the user's files. However, while many generic malware detection systems have been proposed, none of these systems have attempted to specifically address the ransomware detection problem.
In this paper, we present a novel dynamic analysis system called UNVEIL that is specifically designed to detect ransomware. The key insight of the analysis is that in order to mount a successful attack, ransomware must tamper with a user's files or …