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Real-World Sybil Attacks in Bittorrent Mainline DHT

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Real-World Sybil Attacks in Bittorrent Mainline DHT Real-World Sybil Attacks in BitTorrent Mainline DHT Liang Wang † Jussi Kangasharju †‡ †Department of Computer Science, University of Helsinki, Finland ‡Helsinki Institute for Information Technology, University of Helsinki, Finland www.helsinki.fi/yliopisto 1 Sunday, May 19, 2013 Contents Background Measurement Platform Types of Attacks Honeypot Design Real-World Attacks Threats & Solutions Conclusion www.helsinki.fi/yliopisto 2 Sunday, May 19, 2013 BitTorrent MLDHT BitTorrent is the most influential P2P software BitTorrent adopted DHT to support trackless mode More reliable and robust to single point of failure Avoid legal issues and becoming the lawyer’s target Two incompatible versions Mainline DHT (MLDHT) Vuze DHT Both are Kademlia-based DHT www.helsinki.fi/yliopisto 3 Sunday, May 19, 2013 BitTorrent MLDHT Building block of modern P2P software More and more P2P softwares supports MLDHT, over 16,000,000 users Forms a peculiar ecosystem Different implementation has slightly different interpretation of the standard protocol Only minimum functionalities of Kademlia MLDHT is simple but weak www.helsinki.fi/yliopisto 4 Sunday, May 19, 2013 Measurement Platform Two dedicated machines monitor the system Prevent the “sample gap” due to soft- and hardware failure Two crawlers with different crawling policy Continuously take “snapshot” of MLDHT 15 mins interval, started since 2010-12-07 Over 67,000 samples are collected www.helsinki.fi/yliopisto 5 Sunday, May 19, 2013 Measurement Platform A full-fledged monitoring system Five main components Automatically collect and analyze the sample Together with several honeypots to catch specific attacks MLDHT Monitor System Visualizer Crawler Analyzer Maintainer Injector www.helsinki.fi/yliopisto 6 Sunday, May 19, 2013 Two Basic Attacks - Sybil Attack First introduced by Douceur in “The Sybil Attack” in 2002 Inject multiple fake identities into the system Use them as a starting point to perform further attacks Can also be considered as routing table attack www.helsinki.fi/yliopisto 7 Sunday, May 19, 2013 Two Basic Attacks Horizontal Attack Spread sybils widely across the system Pollute as many routing table as possible Vertical Attack Isolate an node by filling routing table with malicious nodes Target can be content (more general than Eclipse Attack) Hybrid Attack Combined both Horizontal and Vertical attacks www.helsinki.fi/yliopisto 8 Sunday, May 19, 2013 BitTorrent MLDHT - Four Control Messages PING ‒ Probe a node’s availability. FIND_NODE ‒ Given a target ID, find the K closest neighbors of the ID. GET_PEERS ‒ given an infohash, get the initial peer set. ANNOUNCE_PEER ‒ a peer announces it belongs to a swarm. www.helsinki.fi/yliopisto 9 Sunday, May 19, 2013 Normal Operation Peer 11 Peer 95 A (Peer 29) 4 Peer 33 C (Peer 82) BT Protocol 1 2 Announce Peer (29,59) Peer 78 Get Peers Peer 36 (82,59) 3 Peer 71 Peer 43 Peer 65 Peer 51 B (Peer 57) www.helsinki.fi/yliopisto 10 Sunday, May 19, 2013 Two Basic Attacks - Horizontal Attack Peer 11 Peer 95 Peer 29 Find Node Peer 33 Peer 82 (29,78) I am 78 Find Node (82,57) Peer 78 Peer 36 1 Find Node I am 57 (43,65) I am 65 2 Peer 71 Peer 43 Peer 65 Peer 51 Peer 57 www.helsinki.fi/yliopisto 11 Sunday, May 19, 2013 Two Basic Attacks - Horizontal Attack Horizontal attack spreads sybils widely across the system The aim is to pollute as many routing tables as possible The number of sybils in one routing table is not the concern A successful horizontal attack can let the attacker sniff most of the control messages and therefore hijack the system In MLDHT, this attack can be carried out with very limited physical resources www.helsinki.fi/yliopisto 12 Sunday, May 19, 2013 Two Basic Attacks - Vertical Attack Peer 11 Peer 95 Peer 29 Peer 33 Peer 82 1 Get Peers (82,59) Announce Peer (29,59) Peer 78 3 2 Peer 36 BT Protocol Sybil Sybil Peer 43 Peer 71 Sybil Sybil 4 Sybil Peer 65 Peer 51 Peer 57 www.helsinki.fi/yliopisto 13 Sunday, May 19, 2013 Two Basic Attacks - Vertical Attack Vertical attack attempts to insert as many sybils as possible in one specific routing table. Similar to eclipse attack, but broader in the sense it can target content After launching an attack, the attacker waits for an interesting target ID, either node ID or content infohash. Then, the attacker inserts sybils close to the target to ”isolate” it from the others. www.helsinki.fi/yliopisto 14 Sunday, May 19, 2013 Honeypot Design - Three Types of Honeypots Detector ‒ First round filtering, identifying suspicious nodes ‒ Work on the MLDHT protocol level MLDHT honeypot ‒ Second round filtering, identify vertical and hybrid attacks ‒ Work on the MLDHT protocol level BitTorrent honeypot ‒ Work on the BitTorrent protocol level ‒ Identify further malicious behaviors www.helsinki.fi/yliopisto 15 Sunday, May 19, 2013 Honeypot Design - Three Types of Honeypots Detector First round filtering, identifying suspicious nodes Use FIND_NODE to find “non-existent” ID in MLDHT ‒ If some node claims as the owner of the ID ---> Suspicious! Use GET_PEERS to find “non-existent” infohash in MLDHT ‒ if someone comes to us with those IDs ---> Suspicious! Try to catch horizontal attacks ‒ because in reality, horizontal attack is the starting point of a successful large-scale attack www.helsinki.fi/yliopisto 16 Sunday, May 19, 2013 Honeypot Design - MLDHT Honeypot MLDHT honeypot Detect vertical and hybrid attacks Suppose our own ID is x, use GET_PEERS to find x+1 ‒ Not such content with infohash x+1 at all in MLDHT ‒ Normal behavior is replying with k nodes with closest ID ‒ However, lots of nodes came and used “scrape” to probe us ‒ Some immediately started vertical attacks by inserting sybils ‒ Some tried to set up BT level connection to get the metainfo www.helsinki.fi/yliopisto 17 Sunday, May 19, 2013 Honeypot Design - BitTorrent Honeypot BitTorrent honeypot Work on the BitTorrent protocol level Third round filtering, check if there are further actions Most tried to get the metainfo for the infohash But nobody really tried to retrieve any data www.helsinki.fi/yliopisto 18 Sunday, May 19, 2013 Real-World Attacks Two main players (or attacker?) Mr. ISP and Mr. 50 Suspicious behavior, but not really malicious (depends on the standards) Quite amount of smaller players from various orgs www.helsinki.fi/yliopisto 19 Sunday, May 19, 2013 Real-World Attacks - Mr. 50 Two (or more) virtual nodes from Amazon EC2 platform large-scale horizontal attacks The one with IP starting with 50 was the most active one The app was optimized to perform horizontal attack Not maintain states for the nodes Only answer certain messages in order to stay in RT Collect infohashes, later other nodes will get metainfo Like a virus, even the honest node can help propagate www.helsinki.fi/yliopisto 20 Sunday, May 19, 2013 Real-World Attacks - Mr. 50 Very active since the beginning of 2011 We can see the clear “test phase” and “deploy phase” www.helsinki.fi/yliopisto 21 Sunday, May 19, 2013 Real-World Attacks - Mr. 50 Very active since the beginning of 2011 We can see the clear “test phase” and “deploy phase” 5 x 10 3 Mr.50 2.5 Mr.184 2 1.5 # of sybils 1 0.5 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec www.helsinki.fi/yliopisto 21 Sunday, May 19, 2013 Real-World Attacks - Mr. ISP Several ISPs perform intensive “vertical attacks” Very resourceful Further investigation shows the main purpose is to localize BitTorrent traffic www.helsinki.fi/yliopisto 22 Sunday, May 19, 2013 Real-World Attacks - Mr. ISP Several ISPs perform intensive “vertical attacks” Very resourceful Further investigation shows the main purpose is to localize BitTorrent traffic 1 insider 0.8 outsider 0.6 0.4 0.2 Percent of native nodes 0 1 2 3 4 5 6 7 8 File Index www.helsinki.fi/yliopisto 22 Sunday, May 19, 2013 Real-World Attacks - Mr. ISP insider - connect to MLDHT with an IP in the ISP network outsider - connect to MLDHT with an IP outside ISP native node - node in the same ISP network www.helsinki.fi/yliopisto 23 Sunday, May 19, 2013 Real-World Attacks - Mr. ISP insider - connect to MLDHT with an IP in the ISP network outsider - connect to MLDHT with an IP outside ISP native node - node in the same ISP network 1 insider 0.8 outsider 0.6 0.4 0.2 Percent of native nodes 0 1 2 3 4 5 6 7 8 File Index www.helsinki.fi/yliopisto 23 Sunday, May 19, 2013 Threats & Analysis Monitor a large fraction of user activities and traffic Can disturb operation of system Pollute or even effectively censor certain content Hijack system with limited resource is possible Violate user privacy www.helsinki.fi/yliopisto 24 Sunday, May 19, 2013 Threats & Analysis The trend of sybil attack is increasing 5 x 10 Mr.184: 3% 3 Other: 14% 2.5 2 1.5 # of sybils 1 Mr.50: 56% Mr.ISP: 27% 0.5 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec www.helsinki.fi/yliopisto 25 Sunday, May 19, 2013 Possible Solutions Root of the problem - Letting a node choose its own ID Weakness has been well-understood over a decade, but the problem is still there Various solutions, but no silver bullet central, trusted authority to issue ID charge money on ID introduce social network into the system www.helsinki.fi/yliopisto 26 Sunday, May 19, 2013 Conclusion Introduce two basic attacks in MLDHT Hybrid attack can hijack whole system with limited physical resources Extensive measurements to identify real-world attacks Analyze potential damage and discuss possible solutions www.helsinki.fi/yliopisto 27 Sunday, May 19, 2013 Thanks! Questions? www.helsinki.fi/yliopisto 28 Sunday, May 19, 2013.
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