arXiv subjects

Claude Castelluccia

Publications and source records attributed to Claude Castelluccia.

23 records · Page 2Linked to original sources

arXiv2011

How Unique and Traceable are Usernames?

Suppose you find the same username on different online services, what is the probability that these usernames refer to the same physical person? This work addresses what appears to be a fairly simple question, which has many implications for anonymity and privacy on the Internet. One possible way of estimating this probability would be to look at the public information associated to the two accounts and try to match them. However, for most services, these information are chosen by the users themselves and are often very heterogeneous, possibly false and difficult to collect. Furthermore, several websites do not disclose any additional public information about users apart from their usernames (e.g., discus- sion forums or Blog comments), nonetheless, they might contain sensitive information about users. This paper explores the possibility of linking users profiles only by looking at their usernames. The intuition is that the probability that two usernames refer to the same physical person strongly depends on the "entropy" of the username string itself. Our experiments, based on crawls of real web services, show that a significant portion of the users' profiles can be linked using their usernames. To the best of our knowledge, this is the first time that usernames are considered as a source of information when profiling users on the Internet.

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arXiv2011

One Bad Apple Spoils the Bunch: Exploiting P2P Applications to Trace and Profile Tor Users

Tor is a popular low-latency anonymity network. However, Tor does not protect against the exploitation of an insecure application to reveal the IP address of, or trace, a TCP stream. In addition, because of the linkability of Tor streams sent together over a single circuit, tracing one stream sent over a circuit traces them all. Surprisingly, it is unknown whether this linkability allows in practice to trace a significant number of streams originating from secure (i.e., proxied) applications. In this paper, we show that linkability allows us to trace 193% of additional streams, including 27% of HTTP streams possibly originating from "secure" browsers. In particular, we traced 9% of Tor streams carried by our instrumented exit nodes. Using BitTorrent as the insecure application, we design two attacks tracing BitTorrent users on Tor. We run these attacks in the wild for 23 days and reveal 10,000 IP addresses of Tor users. Using these IP addresses, we then profile not only the BitTorrent downloads but also the websites visited per country of origin of Tor users. We show that BitTorrent users on Tor are over-represented in some countries as compared to BitTorrent users outside of Tor. By analyzing the type of content downloaded, we then explain the observed behaviors by the higher concentration of pornographic content downloaded at the scale of a country. Finally, we present results suggesting the existence of an underground BitTorrent ecosystem on Tor.

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arXiv2010

Compromising Tor Anonymity Exploiting P2P Information Leakage

Privacy of users in P2P networks goes far beyond their current usage and is a fundamental requirement to the adoption of P2P protocols for legal usage. In a climate of cold war between these users and anti-piracy groups, more and more users are moving to anonymizing networks in an attempt to hide their identity. However, when not designed to protect users information, a P2P protocol would leak information that may compromise the identity of its users. In this paper, we first present three attacks targeting BitTorrent users on top of Tor that reveal their real IP addresses. In a second step, we analyze the Tor usage by BitTorrent users and compare it to its usage outside of Tor. Finally, we depict the risks induced by this de-anonymization and show that users' privacy violation goes beyond BitTorrent traffic and contaminates other protocols such as HTTP.

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arXiv2010

Private Information Disclosure from Web Searches. (The case of Google Web History)

As the amount of personal information stored at remote service providers increases, so does the danger of data theft. When connections to remote services are made in the clear and authenticated sessions are kept using HTTP cookies, data theft becomes extremely easy to achieve. In this paper, we study the architecture of the world's largest service provider, i.e., Google. First, with the exception of a few services that can only be accessed over HTTPS (e.g., Gmail), we find that many Google services are still vulnerable to simple session hijacking. Next, we present the Historiographer, a novel attack that reconstructs the web search history of Google users, i.e., Google's Web History, even though such a service is supposedly protected from session hijacking by a stricter access control policy. The Historiographer uses a reconstruction technique inferring search history from the personalized suggestions fed by the Google search engine. We validate our technique through experiments conducted over real network traffic and discuss possible countermeasures. Our attacks are general and not only specific to Google, and highlight privacy concerns of mixed architectures using both secure and insecure connections.

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arXiv2009

Code injection attacks on harvard-architecture devices

Harvard architecture CPU design is common in the embedded world. Examples of Harvard-based architecture devices are the Mica family of wireless sensors. Mica motes have limited memory and can process only very small packets. Stack-based buffer overflow techniques that inject code into the stack and then execute it are therefore not applicable. It has been a common belief that code injection is impossible on Harvard architectures. This paper presents a remote code injection attack for Mica sensors. We show how to exploit program vulnerabilities to permanently inject any piece of code into the program memory of an Atmel AVR-based sensor. To our knowledge, this is the first result that presents a code injection technique for such devices. Previous work only succeeded in injecting data or performing transient attacks. Injecting permanent code is more powerful since the attacker can gain full control of the target sensor. We also show that this attack can be used to inject a worm that can propagate through the wireless sensor network and possibly create a sensor botnet. Our attack combines different techniques such as return oriented programming and fake stack injection. We present implementation details and suggest some counter-measures.

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