NDSS 2018 A Large-scale Analysis of Content Modification by Open HTTP Proxies

NDSS 2018 Session 4A: Measurements
01 A Large-scale Analysis of Content Modification by Open HTTP Proxies

SUMMARY
Open HTTP proxies offer a quick and convenient solution for routing web traffic towards a destination. In contrast to more elaborate relaying systems, such as anonymity networks or VPN services, users can freely connect to an open HTTP proxy without the need to install any special software. Therefore, open HTTP proxies are an attractive option for bypassing IPbased filters and geo-location restrictions, circumventing content blocking and censorship, and in general, hiding the client’s IP address when accessing a web server. Nevertheless, the consequences of routing traffic through an untrusted third party can be severe, while the operating incentives of the thousands of publicly available HTTP proxies are questionable. In this paper, we present the results of a large-scale analysis of open HTTP proxies, focusing on determining the extent to which user traffic is manipulated while being relayed. We have designed a methodology for detecting proxies that, instead of passively relaying traffic, actively modify the relayed content. Beyond simple detection, our framework is capable of macroscopically attributing certain traffic modifications at the network level to well-defined malicious actions, such as ad injection, user fingerprinting, and redirection to malware landing pages. We have applied our methodology on a large set of publicly available HTTP proxies, which we monitored for a period of two months, and identified that 38% of them perform some form of content modification. The majority of these proxies can be considered benign, as they do not perform any harmful content modification. However, 5.15% of the tested proxies were found to perform modification or injection that can be considered as malicious or unwanted. Specifically, 47% of the malicious proxies injected ads, 39% injected code for collecting user information that can be used for tracking and fingerprinting, and 12% attempted to redirect the user to pages that contain malware. Our study reveals the true incentives of many of the publicly available web proxies. Our findings raise several concerns, as we uncover multiple cases where users can be severely affected by connecting to an open proxy. As a step towards protecting users against unwanted content modification, we built a service that leverages our methodology to automatically collect and probe public proxies, and generates a list of safe proxies that do not perform any content modification, on a daily basis.

SLIDES
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PAPER
http://wp.internetsociety.org/ndss/wp...

SLIDES
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AUTHORS
Giorgos Tsirantonakis (FORTH)
Panagiotis Ilia (FORTH), Sotiris Ioannidis (FORTH)
Elias Athanasopoulos (University of Cyprus)
Michalis Polychronakis (Stony Brook University)


Network and Distributed System Security (NDSS) Symposium 2018, 18-21 February 2018, Catamaran Resort Hotel & Spa in San Diego, California.
https://www.ndss-symposium.org/ndss20...


ABOUT NDSS
The Network and Distributed System Security Symposium (NDSS) fosters information exchange among researchers and practitioners of network and distributed system security. The target audience includes those interested in practical aspects of network and distributed system security, with a focus on actual system design and implementation. A major goal is to encourage and enable the Internet community to apply, deploy, and advance the state of available security technologies.
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