Attacking a Swarm with a Band of Liars evaluating the impact of attacks on BitTorrent

Transcription

1 Attacking a Swarm with a Band of Liars evaluating the impact of attacks on BitTorrent Marlom A. Konrath, Marinho P. Barcellos, Rodrigo B. Mansilha PIPCA Programa de Pós-Graduação em Computação Aplicada Universidade do Vale do Rio dos Sinos (UNISINOS) São Leopoldo, RS Brasil Galway, Sept th IEEE International Conference on P2P

2 Introduction Context: BitTorrent In P2P, file sharing seems to be the killer application BitTorrent is one of the most popular instances of file sharing Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do2 Vale / 31 do

3 Introduction Motivation & Related Work Research efforts have investigated BitTorrent To understand its behavior, expose potential limitations and propose improvements P2P fairness issues and incentive mechanisms There are several attacks reported in the literature But always in peer s self-benefit, like avoiding any contribution to the network In contrast, we emphasize security aspects a malicious peer wants damage to a swarm Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do3 Vale / 31 do

4 Introduction Motivation & Related Work Research efforts have investigated BitTorrent To understand its behavior, expose potential limitations and propose improvements P2P fairness issues and incentive mechanisms There are several attacks reported in the literature But always in peer s self-benefit, like avoiding any contribution to the network In contrast, we emphasize security aspects a malicious peer wants damage to a swarm Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do3 Vale / 31 do

5 Introduction Our Aims in This Paper Identification of attacks exploiting vulnerabilities of the BitTorrent protocol Evaluation of their impact Two specific attacks addressed: piece lying and Eclipse Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do4 Vale / 31 do

6 Rest of the Talk Introduction 1 BitTorrent 2 Attack and Subversion Strategies 3 BitTorrent Simulation 4 Impact Evaluation 5 Concluding Remarks Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do5 Vale / 31 do

7 Outline BitTorrent 1 BitTorrent 2 Attack and Subversion Strategies 3 BitTorrent Simulation 4 Impact Evaluation 5 Concluding Remarks Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do6 Vale / 31 do

8 BitTorrent Main Elements.torrent file Trackers Seeders Leechers Swarm Pieces Blocks Bitfields Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do7 Vale / 31 do

9 BitTorrent Policies and Strategies Connection policies: peer obtains peer IPs from the tracker and maintains a number of connections with other peers Tit-for-tat: incentive mechanism to increase collaboration Local Rarest First (LRF): peer selects for download the piece that looks rarest Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do8 Vale / 31 do

10 State Diagrams 1/3 BitTorrent Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do9 Vale / 31 do

11 State Diagrams 2/3 BitTorrent Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 10 Vale / 31 do

12 State Diagrams 3/3 BitTorrent Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 11 Vale / 31 do

13 Outline Attack and Subversion Strategies 1 BitTorrent 2 Attack and Subversion Strategies 3 BitTorrent Simulation 4 Impact Evaluation 5 Concluding Remarks Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 12 Vale / 31 do

14 Attack and Subversion Strategies Attack and Subversion Strategies Sybil attack: single physical peer with multiple virtual identities Piece lying Peer eclipsing Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 13 Vale / 31 do

15 Attack and Subversion Strategies Piece Lying Attack LRF aims to equalize the number of copies of each piece in the swarm Attack aims to interfere with this balance Malicious peer lies about having one or more pieces, but never unchokes other peers Many peers acting in collusion and lying about certain pieces induce the non-malicious peers to choose other pieces first This tends to make certain pieces artificially rarer When pieces become less common, it may slow down the swarm or even cause a swarm failure Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 14 Vale / 31 do

16 Attack and Subversion Strategies Peer Eclipse Attack In BitTorrent each peer usually connects to a limited number of peers A malicious peer does not collaborate (or might collaborate very little) Malicious peers connect to correct peers (and are connected by correct peers) The list of peers a correct peer knows about is randomly taken from trackers, and there will be malicious and correct peers If a correct peer is connected to malicious peers only, then it is Eclipsed It makes no progress and eventually fails Even if there are some correct peers connected, the download will take longer or even fail if peers leave Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 15 Vale / 31 do

17 Outline BitTorrent Simulation 1 BitTorrent 2 Attack and Subversion Strategies 3 BitTorrent Simulation 4 Impact Evaluation 5 Concluding Remarks Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 16 Vale / 31 do

18 Basic Aspects BitTorrent Simulation Studied the protocol specification, implementations and the literature Created a simulation model of a swarm Reflects the detailed behavior of peers Extension of a simulation framework called Simmcast (written in Java) Modeled elements and input parameters: number and type of peers, the way they arrive to the swarm, bandwidth, contribution rate, and so on Assumptions: single tracker, no detailed TCP modeling Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 17 Vale / 31 do

19 BitTorrent Simulation Is the Simulator any Real? SImulation results produced without attack were consistent with measurements reported in the literature matched experimental results obtained from a small, controlled environment experimented with different content sizes, piece size in blocks, bandwidth, and number of peers Packets were collected using passive monitoring Results showed similarity Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 18 Vale / 31 do

20 Outline Impact Evaluation 1 BitTorrent 2 Attack and Subversion Strategies 3 BitTorrent Simulation 4 Impact Evaluation 5 Concluding Remarks Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 19 Vale / 31 do

21 Questions Posed Impact Evaluation 1 What is the impact of the Piece Lying attack on the dynamics of a swarm, when compared to the case without attack? 2 What happens when the number of liars increases? 3 In the Eclipse attack, which number of Sybils is more effective and why? Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 20 Vale / 31 do

22 Questions Posed Impact Evaluation 1 What is the impact of the Piece Lying attack on the dynamics of a swarm, when compared to the case without attack? 2 What happens when the number of liars increases? 3 In the Eclipse attack, which number of Sybils is more effective and why? Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 20 Vale / 31 do

23 Questions Posed Impact Evaluation 1 What is the impact of the Piece Lying attack on the dynamics of a swarm, when compared to the case without attack? 2 What happens when the number of liars increases? 3 In the Eclipse attack, which number of Sybils is more effective and why? Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 20 Vale / 31 do

24 Impact Evaluation Model Parameters and Assumptions Analysis focused on the first hours of a swarm 1 initial seeder 100 leechers that arrive following Exponential distribution Contribution rate equals 1.0 for leecher and 2.0 for seeder Reconnection between peer and tracker at every 30s Shared content 640MB = 640 pieces of 1MB, each with of 64 blocks of 16 KB Leechers have a maximum download time (10x average time) Asymmetric bandwidths: download 1 Mbps and upload 256 Kbps Malicious peers act in collusion and start the attack at the same moment (on 5th peer) Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 21 Vale / 31 do

25 Impact Evaluation Swarm with Normal Behavior 100 Seeders Leechers Remaining L max =59 Peers S max = Time (minutes) L max = maximum number of leechers reached S max = maximum number of seeders reached Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 22 Vale / 31 do

26 Impact Evaluation Evaluation Metrics Increase in download time Number of download failures (as users give up) Complete swarm failure Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 23 Vale / 31 do

27 Impact Evaluation Impact of the Piece Lying attack? 25 liars lying about 4 pieces 100 Seeders Leechers Remaining 100 Seeders Leechers Remaining L max =77 60 L max =59 60 Peers Peers S max =10 20 S max = Time (minutes) Time (minutes) Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 24 Vale / 31 do

28 Impact Evaluation What happens when the number of liars increases? Peers lying about a set of 32 pieces Number of Downloads Completed Liars 1 Liars 5 Liars Liars 15 Liars 20 Liars 25 Liars Liars 75 Liars 100 Liars Download time (minutes) Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 25 Vale / 31 do

29 Impact Evaluation In Eclipse, which number of Sybils is more efficient? Varying the number of Sybils connecting randomly Number of Downloads Completed Sybils 10 Sybils Sybils 25 Sybils 30 Sybils Sybils 50 Sybils 60 Sybils Sybils 80 Sybils 90 Sybils 100 Sybils Sybils 300 Sybils 400 Sybils Sybils 600 Sybils 1000 Sybils Download time (minutes) Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 26 Vale / 31 do

30 Impact Evaluation Impact of Eclipse Example depicts swarm under attack of a gang of 50 Sybils 100 Seeders Leechers Remaining L max =95 Seeders Leechers Remaining L max =59 60 Peers Peers S max =10 10 S max = Time (minutes) Time (minutes) Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 27 Vale / 31 do

31 Outline Concluding Remarks 1 BitTorrent 2 Attack and Subversion Strategies 3 BitTorrent Simulation 4 Impact Evaluation 5 Concluding Remarks Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 28 Vale / 31 do

32 Concluding Remarks Conclusions Novelty is to address security in BitTorrent in the sense of causing harm Presented a simulation evaluation of the impact of two attacks Discrete-event simulator produced results were compared with experimental data Results indicate that a modest set of resources can be used to launch an attack and harm a BitTorrent network Attack of piece lying seems effective with 50 or more liars in the configuration evaluated Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 29 Vale / 31 do

33 Concluding Remarks Future Work There are many opportunities for future work There are other relevant attacks and security issues Impact of attacks needs to be evaluated with large scale simulations Experimental evaluation of attacks with different user agents to validate results Project, implementation and evaluation of counter-measures Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 30 Vale / 31 do

34 Concluding Remarks Contatcts Thank you. Prof. Marinho P. Barcellos or marinho P2P-SeC: Secure and reliable Computing in P2P networks PIPCA/UNISINOS Brazil Marinho P. Barcellos - P2P-SeC - UNISINOS ( PIPCA Programa Attacking de BitTorrent Pós-Graduação em Computação Aplicada Universidade do 31 Vale / 31 do