Nick Nikiforakis

FPDetective: dusting the web for fingerprinters

In the modern web, the browser has emerged as the vehicle of choice, which users are to trust, customize, and use, to access a wealth of information and online services. However, recent studies show that the browser can also be used to invisibly fingerprint the user: a practice that may have serious privacy and security implications. In this paper, we report on the design, implementation and deployment of FPDetective, a framework for the detection and analysis of web-based fingerprinters. Instead of relying on information about known fingerprinters or third-party-tracking blacklists, FPDetective focuses on the detection of the fingerprinting itself. By applying our framework with a focus on font detection practices, we were able to conduct a large scale analysis of the million most popular websites of the Internet, and discovered that the adoption of fingerprinting is much higher than previous studies had estimated. Moreover, we analyze two countermeasures that have been proposed to defend against fingerprinting and find weaknesses in them that might be exploited to bypass their protection. Finally, based on our findings, we discuss the current understanding of fingerprinting and how it is related to Personally Identifiable Information, showing that there needs to be a change in the way users, companies and legislators engage with fingerprinting.

FlowFox: a web browser with flexible and precise information flow control

We present FlowFox, the first fully functional web browser that implements a precise and general information flow control mechanism for web scripts based on the technique of secure multi-execution. We demonstrate how FlowFox subsumes many ad-hoc script containment countermeasures developed over the last years. We also show that FlowFox is compatible with the current web, by investigating its behavior on the Alexa top-500 web sites, many of which make intricate use of JavaScript. The performance and memory cost of FlowFox is substantial (a performance cost of around 20% on macro benchmarks for a simple two level policy), but not prohibitive. Our prototype implementation shows that information flow enforcement based on secure multi-execution can be implemented in full-scale browsers. It can support powerful, yet precise policies refining the same-origin-policy in a way that is compatible with existing websites.

SessionShield: lightweight protection against session hijacking

The class of Cross-site Scripting (XSS) vulnerabilities is the most prevalent security problem in the field of Web applications. One of the main attack vectors used in connection with XSS is session hijacking via session identifier theft. While session hijacking is a client-side attack, the actual vulnerability resides on the server-side and, thus, has to be handled by the websites operator. In consequence, if the operator fails to address XSS, the applications users are defenseless against session hijacking attacks. In this paper we present SessionShield, a lightweight client-side protection mechanism against session hijacking that allows users to protect themselves even if a vulnerable websites operator neglects to mitigate existing XSS problems. SessionShield is based on the observation that session identifier values are not used by legitimate clientside scripts and, thus, need not to be available to the scripting languages running in the browser. Our system requires no training period and imposes negligible overhead to the browser, therefore, making it ideal for desktop and mobile systems.

RIPE: runtime intrusion prevention evaluator

Despite the plethora of research done in code injection countermeasures, buffer overflows still plague modern software. In 2003, Wilander and Kamkar published a comparative evaluation on runtime buffer overflow prevention technologies using a testbed of 20 attack forms and demonstrated that the best prevention tool missed 50% of the attack forms. Since then, many new prevention tools have been presented using that testbed to show that they performed better, not missing any of the attack forms. At the same time though, there have been major developments in the ways of buffer overflow exploitation. In this paper we present RIPE, an extension of Wilanders and Kamkars testbed which covers 850 attack forms. The main purpose of RIPE is to provide a standard way of testing the coverage of a defense mechanism against buffer overflows. In order to test RIPE we use it to empirically evaluate some of the newer prevention techniques. Our results show that the most popular, publicly available countermeasures cannot prevent all of RIPEs buffer overflow attack forms. ProPolice misses 60%, LibsafePlus+TIED misses 23%, CRED misses 21%, and Ubuntu 9.10 with nonexecutable memory and stack protection misses 11%.

Stranger danger: exploring the ecosystem of ad-based URL shortening services

URL shortening services facilitate the need of exchanging long URLs using limited space, by creating compact URL aliases that redirect users to the original URLs when followed. Some of these services show advertisements (ads) to link-clicking users and pay a commission of their advertising earnings to link-shortening users. In this paper, we investigate the ecosystem of these increasingly popular ad-based URL shortening services. Even though traditional URL shortening services have been thoroughly investigated in previous research, we argue that, due to the monetary incentives and the presence of third-party advertising networks, ad-based URL shortening services and their users are exposed to more hazards than traditional shortening services. By analyzing the services themselves, the advertisers involved, and their users, we uncover a series of issues that are actively exploited by malicious advertisers and endanger the users. Moreover, next to documenting the ongoing abuse, we suggest a series of defense mechanisms that services and users can adopt to protect themselves.

Serene: self-reliant client-side protection against session fixation

The web is the most wide-spread and de facto distributed platform, with a plethora of valuable applications and services. Building stateful services on the web requires a session mechanism that keeps track of server-side session state, such as authentication data. These sessions are an attractive attacker target, since taking over an authenticated session fully compromises the users account. This paper focuses on session fixation, where an attacker forces the user to use the attackers session, allowing the attacker to take over the session after authentication. We present Serene, a self-reliant client-side countermeasure that protects the user from session fixation attacks, regardless of the security provisions --- or lack thereof --- of a web application. By specifically protecting session identifiers from fixation and not interfering with other cookies or parameters, Serene is able to autonomously protect a large majority of web applications, without being disruptive towards legitimate functionality. We experimentally validate these claims with a large scale study of Alexas top one million sites, illustrating both Serenes large coverage (83.43%) and compatibility (95.55%).

Bitsquatting: exploiting bit-flips for fun, or profit?

Over the last fifteen years, several types of attacks against domain names and the companies relying on them have been observed. The well-known cybersquatting of domain names gave way to typosquatting, the abuse of a users mistakes when typing a URL in her browsers address bar. Recently, a new attack against domain names surfaced, namely bitsquatting. In bitsquatting, an attacker leverages random bit-errors occurring in the memory of commodity computers and smartphones, to redirect Internet traffic to attacker-controlled domains. In this paper, we report on a large-scale experiment, measuring the adoption of bitsquatting by the domain-squatting community through the tracking of registrations of bitsquatting domains targeting popular web sites over a 9-month period. We show how new bitsquatting domains are registered daily and how attackers are trying to monetize their domains through the use of ads, abuse of affiliate programs and even malware installations. Lastly, given the discovered prevalence of bitsquatting, we review possible defense measures that companies, software developers and Internet Service Providers can use to protect against it.

A Dangerous Mix: Large-Scale Analysis of Mixed-Content Websites

In this paper, we investigate the current state of practice about mixed-content websites, websites that are accessed using the HTTPS protocol, yet include some additional resources using HTTP. Through a large-scale experiment, we show that about half of the Internets most popular websites are currently using this practice and are thus vulnerable to a wide range of attacks, including the stealing of cookies and the injection of malicious JavaScript in the context of the vulnerable websites. Additionally, we investigate the default behavior of browsers on mobile devices and show that most of them, by default, allow the rendering of mixed content, which demonstrates that hundreds of thousands of mobile users are currently vulnerable to MITM attacks.

Soundsquatting: Uncovering the Use of Homophones in Domain Squatting

In this paper we present soundsquatting, a previously unreported type of domain squatting which we uncovered during analysis of cybersquatting domains. In soundsquatting, an attacker takes advantage of homophones, i.e., words that sound alike, and registers homophone-including variants of popular domain names. We explain why soundsquatting is different from existing domain-squatting attacks, and describe a tool for the automatic generation of soundsquatting domains. Using our tool, we discover that attackers are already aware of the principles of soundsquatting and are monetizing them in various unethical and illegal ways. In addition, we register our own soundsquatting domains and study the population of users who reach our monitors, recording a monthly average of more than 1,700 non-bot page requests. Lastly, we show how sound-dependent users are particularly vulnerable to soundsquatting through the abuse of text-to-speech software.

The Clock is Still Ticking: Timing Attacks in the Modern Web

Web-based timing attacks have been known for over a decade, and it has been shown that, under optimal network conditions, an adversary can use such an attack to obtain information on the state of a user in a cross-origin website. In recent years, desktop computers have given way to laptops and mobile devices, which are mostly connected over a wireless or mobile network. These connections often do not meet the optimal conditions that are required to reliably perform cross-site timing attacks. In this paper, we show that modern browsers expose new side-channels that can be used to acquire accurate timing measurements, regardless of network conditions. Using several real-world examples, we introduce four novel web-based timing attacks against modern browsers and describe how an attacker can use them to obtain personal information based on a users state on a cross-origin website. We evaluate our proposed attacks and demonstrate that they significantly outperform current attacks in terms of speed, reliability, and accuracy. Furthermore, we show that the nature of our attacks renders traditional defenses, i.e., those based on randomly delaying responses, moot and discuss possible server-side defense mechanisms.