Reflection Scan: an Off-Path Attack on TCP

TL;DR

This paper introduces Reflection Scan, a novel off-path attack exploiting shared queue load as a side channel to leak information from TCP and other protocols by analyzing induced processing delays.

Contribution

It presents a new off-path attack method using traffic load as a side channel, demonstrating its effectiveness against TCP and other protocols.

Findings

Effective in revealing protected information via shared queue load

Applicable to TCP and potentially other protocols

Proof of concept confirms real-world feasibility

Abstract

The paper demonstrates how traffic load of a shared packet queue can be exploited as a side channel through which protected information leaks to an off-path attacker. The attacker sends to a victim a sequence of identical spoofed segments. The victim responds to each segment in the sequence (the sequence is reflected by the victim) if the segments satisfy a certain condition tested by the attacker. The responses do not reach the attacker directly, but induce extra load on a routing queue shared between the victim and the attacker. Increased processing time of packets traversing the queue reveal that the tested condition was true. The paper concentrates on the TCP, but the approach is generic and can be effective against other protocols that allow to construct requests which are conditionally answered by the victim. A proof of concept was created to assess applicability of the method in real-life scenarios.