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Title: A Forensically Sound Method of Identifying Downloaders and Uploaders in Freenet
The creation and distribution of child sexual abuse materials (CSAM) involves a continuing violation of the victims? privacy beyond the original harms they document. A large volume of these materials is distributed via the Freenet anonymity network: in our observations, nearly one third of requests on Freenet were for known CSAM. In this paper, we propose and evaluate a novel approach for investigating these violations of exploited children's privacy. Our forensic method distinguishes whether or not a neighboring peer is the actual uploader or downloader of a file or merely a relayer. Our method requires analysis of the traffic sent to a single, passive node only. We evaluate our method extensively. Our in situ measurements of actual CSAM requests show an FPR of 0.002 ± 0.003 for identifying downloaders. And we show an FPR of 0.009 ± 0.018, a precision of 1.00 ± 0.01, and a TPR of 0.44 ± 0.01 for identifying uploaders based on in situ tests. Further, we derive expressions for the FPR and Power of our hypothesis test; perform simulations of single and concurrent downloaders; and characterize the Freenet network to inform parameter selection. We were participants in several United States Federal Court cases in which the use of our method was uniformly upheld.  more » « less
Award ID(s):
1816851
PAR ID:
10281425
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security
Page Range / eLocation ID:
1497 to 1512
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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