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Community-enhanced De-anonymization of Online
Social Networks
Shirin Nilizadeh, Apu Kapadia, Yong-Yeol AhnIndiana University Bloomington
CCS 2014
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Online Social Networks (OSNs) have revolutionized
the way our society communicates
1.28 Billion
540 million
225 million
187 million
Monthly active users
40million
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Reference: http://www.domo.com/blog/2014/04/data-never-sleeps-2-0/
OSN providers have become
treasure troves of information
for marketers and
researchers
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Reference: http://datasift.com
Social Data platforms gather, filter and deliver social data to
enterprise-scale companies
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Also, OSN providers publish their ‘anonymized’ social data for competitions and challenges
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Several works have shown that this ‘anonymized’ published data can be
de-anonymized
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The Kaggle social network challenge: Link prediction on an anonymized
dataset
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Crawled Flickr and matched users of two public and anonymized Flickr
networks
[Narayanan and Shmatikov, 2009]
Public Flickr Network Anonymized Flickr Network
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De-anonymizing a social network using another public social network
Flickr Network Twitter Network
Alice
BobCarol
Eve
Rob
John
Republican
Republican
Democrat
Democrat
Democrat
Republican
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Narayanan and Shmatikov’s (NS) de-anonymization approach
1- Seed identification2- Propagation
Reference Network Anonymized Network
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Seed identification• that randomly samples a subset of k-cliques
from the reference graph and finds the corresponding cliques in the other graph.
• the degree sequence of the k nodes in the given clique and the number of common neighbors between each of C(k,2) pairs of users
• compares the two sequences and decides based on an error parameter, whether they are the same people or not
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Propagation
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Network communities provide an effective way to divide-and-conquer
the problem
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Comm-aware vs. Comm-blind
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Step 1- Community Detection: slicing the network into smaller, dense chunks
Reference Network Anonymized Network
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Step 2- Creating graph of communities and mapping communities
Reference Network Anonymized Network
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Step 2- Creating graph of communities and mapping communities
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Step 3- Seed enrichment and local propagation
Identifying more seeds using nodes’ degrees and clustering coefficients
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Step 3- Seed enrichment and local propagation
The clustering coefficient is a property of a node in a network and quantifies how close its neighbors are to being a clique
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Step 4- Global propagation further extends the mapping
Reference Network Anonymized Network
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We tested our approach on real-world datasets
Real-world data set Number of Nodes
Number of edges
arXiv collaboration network 36,458 171,735
Twitter mention network 1 90,332 377,588
Twitter mention network 2 9,745 50,164
Used the METIS graph partitioning algorithm to obtain a smaller network
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Generating noisy anonymized networks with same set of nodes and different but
overlapping set of edges
- Noise level: {0.1%, 1%, 5%, 10%, 15%, 20%, 30%, 40%}
- Generated an ensemble of 10 networks for each network
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Measuring performance using success rate and error rate
With 20% edge noise and 16 seeds, the NS maps can barely maps any node while,our approach maps 40% of the nodes
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Need to consider information gain: degree of anonymity
In practice, the mapping algorithm may still leave several nodes unmapped. For these unmapped nodes, however, the community structure reveals information about the true mapping
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What is the degree
of anonymity for Waldo?
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Degree of anonymity for Wlado degrades knowing that he loves socks!
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Calculating degree of anonymity
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Calculating degree of anonymity• The anonymity for a user u is the entropy over the probability
distribution of potential mappings being true for user u:
• The normalized degree of anonymity for user u:
• The degree of anonymity for the whole system:
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Calculating degree of anonymity: Case 1
0.80.01
0.01
0.01
0.01
0.010.010.01
0.01
0.010.01
0.01
0.01
0.01 0.01
0.01
0.01
0.01
0.80.003 0.003
0.003
0.003
0.0030.003
0.003
0.003
0.003 0.003
0.003
0.003
0.003
0.037
0.037
0.037
0.037
Comm-blind Comm-aware
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Community-aware algorithm greatly improves de-anonymization
performance under noise
With 15% edge noise and 16 seeds, the comm-blind technique reduces anonymity by 2.6 bits, whereas our approach reduces anonymity by 13.17 bits
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Community-aware algorithm is more robust to larger network size and a
low number of seeds
For the Twitter dataset with 90K nodes, with 10% edge noise and only 4 seeds, the comm-blind technique reduces anonymity by 2.14 bits, whereas our approach reduces anonymity by 15.97 bits
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Limitations• We didn’t have access to two real-world social
network data sets with the overlapping sets of users and edges
• Our measure is estimating the upper bound of the degree of anonymity
• We approximate the real probabilities for calculating degree of anonymity by running simulations
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Future work
• Advanced anonymization techniques are required
• Our approach can be improved by use of additional attributes for re-identifying communities and users
• Test other anonymization techniques using comm-aware de-anonymization approach
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Conclusion• Our approach divides the problem into smaller sub-
problems that can be solved by leveraging existing network alignment methods recursively on multiple levels
• Our approach is more robust against added noise to the anonymized data set, and can perform well with fewer known seeds as well as larger networks.
• We analyzed the ‘degree of anonymity’ of users in the graph and showed that the mapping of communities may markedly reduce the degree of anonymity of users.
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THANK YOU! QUESTIONS?