Detecting Collusive Cheating in Online Shopping
Systems through Characteristics of Social Networks
Jianwei Niu
1
, Lei Wang
1
, Yixin Chen
2
, Wenbo He
2
State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing 100191, China
1
,
McGill University, Canada
2
niujianwei@buaa.edu.cn, wangleildmc@gmail.com, chenyixinabel@gmail.com, wenbohe@gmail.com
Abstract—Detecting the collaborative cheating in an online
shopping system is an important but challenging issue. In this
paper, we propose a novel approach to detect the collusive
manipulation on ratings in Amazon, an online shopping system.
Rather than focusing on rating values, we believe the online
shopping and rating activities have nontrivial attributes in terms
of social network connections. Our major contributions include:
(a) We build a virtual social network based on users’ ratings and
comments, and detect the collusive cheating based on the social
network activities. (b) We investigate the properties of disconnect-
ed components in a wide range of social networks, such as the
longevity and final size of the disconnected components before
they join the giant connected component or merge with other
disconnected components. (c) We apply our proposed collusion
detection algorithm to detect the possible collusive cheating on
the ratings based on the data we crawl from Amazon, and the
experimental results validate our approach.
I. INTRODUCTION
With the increase of the popularity and scale of the online
shopping systems such as Amazon, eBay and Taobao, reputa-
tion systems have been widely deployed to protect the honest
buyers and the reputable sellers through the customer ratings,
reviews, and the user recommendations and referrals. However,
the reputation systems are in general vulnerable to many types
of attacks [6], where selfish users try to manipulate the rating. A
typical example is that a group of users collaboratively subvert
the rating of a given product or service. Another example is
so-called Sybil attack [1] where a user creates a large number
of identities and uses them to gain a large influence [9]. With
the desire to promote their own products, users have strong
motivation to cheat by providing unfair ratings.
Detecting the unfair ratings introduced by collaborative ma-
nipulation (from either a single Sybil attacker or a group of
collusive users) is an important but challenging issue. Previous
efforts have been based on the investigation of rating values
[18]. For example, if a rating value is far away from the
majoritys opinion, or if we observe a sudden change of the
rating values in a short time period, there is likely to be an
attack manipulating the rating scores. The rating-value-based
detection schemes usually make several assumptions such as
(1) the number of manipulated ratings is less than the number
of honest ratings; (2) the bias of the manipulated ratings is
sufficiently large; (3) there is no bursty rating input.
In this paper, we propose a novel approach to detect the
collusive manipulation on ratings in real world. Rather than
focusing on rating values, we believe that the online shopping
and rating systems have the common attributes as the online
social networks in terms of social connections. Hence, we
first model the normal behavior of the honest users in online
shopping and rating systems as a user in a virtual social
network, and we identify characteristics of normal users from
a wide range of online social networks. We then check if a
user’s behavior in the virtual social network deviates from the
observed normal behavior to identify suspicious users for future
scrutiny. The contributions of this paper are summarized as
follows:
(1) We build a virtual social network based on users’
ratings and comments, and detect the collusion based on the
characteristics of the virtual social networks. We observe that
collusive users trying to promote or badmouth a specific group
of products, usually by using a special account to do so and
the account may not be used frequently. So in the virtual social
network, if we connect two users when they make similar
comments or ratings on the same product or user, the collusive
users are likely to form disconnected components. By modeling
the collusive users in this way, we employ the characteristics of
online social networks to detect suspicious users in the online
shopping and rating systems.
(2) We investigate the characteristics of the disconnected
components in a wide range of social networks, such as the
longevity and size of the disconnected components. We observe
that the disconnected components exhibit similar characteristics
in different social networks, hence we obtain a generic model
for normal social network users. Then, we detect the collusion
by checking if the disconnected components in the virtual social
network behave significantly different from the model.
(3) To evaluate the proposed approach, we crawl the Amazon
data including 7,659,294 transactions and 123,384 users. We
applied the proposed collusion detection algorithm to detect the
possible collusive manipulation on the ratings, and found 836
suspicious users. After the closer investigation by people, 704
of detected users are considered cheating. We believe that the
proposed approaches have a great impact on collusion detection
in online shopping systems.
The rest of this paper is organized as follows. Section II
introduces the related work in this field. Section III describes
how to model an online shopping and rating system as a virtual
social network. In Section IV, we study a wide range of online
social networks in the real world and show the characteristics of
them. We propose a collusion detection algorithm in Section V,
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