TorMult: Introducing a Novel Tor Bandwidth Inflation Attack
Christoph Sendner, Jasper Stang, Alexandra Dmitrienko, Raveen, Wijewickrama, Murtuza Jadliwala

TL;DR
This paper introduces TorMult, a new bandwidth inflation attack on Tor that exploits resource sharing among relays, enabling attackers to significantly inflate perceived bandwidth and potentially control a large portion of the network.
Contribution
The paper presents a novel attack vector, TorMult, with two variants, demonstrating its effectiveness through private network tests and theoretical analysis.
Findings
Inflates measured bandwidth close to the number of relays in the cluster
Achieves control over half of Tor traffic with just 10 servers and 109 relays
Demonstrates significant threat to Tor's anonymity and resource sharing practices
Abstract
The Tor network is the most prominent system for providing anonymous communication to web users, with a daily user base of 2 million users. However, since its inception, it has been constantly targeted by various traffic fingerprinting and correlation attacks aiming at deanonymizing its users. A critical requirement for these attacks is to attract as much user traffic to adversarial relays as possible, which is typically accomplished by means of bandwidth inflation attacks. This paper proposes a new inflation attack vector in Tor, referred to as TorMult, which enables inflation of measured bandwidth. The underlying attack technique exploits resource sharing among Tor relay nodes and employs a cluster of attacker-controlled relays with coordinated resource allocation within the cluster to deceive bandwidth measurers into believing that each relay node in the cluster possesses ample…
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Taxonomy
TopicsInternet Traffic Analysis and Secure E-voting · Network Security and Intrusion Detection · Full-Duplex Wireless Communications
