2 LITERATURE REVIEW
The following sections will give a brief literature
review over two aspects: the prevalence of account
sharing and existing studies on user authentication
using behavioural biometrics.
2.2.1 Account Sharing
Online account as a kind of personal asset is not
designed to be shared in the first place. However,
people are constantly sharing their accounts as a sign
of trust in a family or a romantic relationship, to take
advantage of the company or simply for convenience
(Obada-Obieh, Huang, & Beznosov, 2020). The
statistics show that in the US, 54% of Americans have
taken part in the account sharing behaviour, of which
the sharing rate of streaming applications like Netflix
and Hulu is up to 75% (Financial country, 2022;
Obada-Obieh, Huang, & Beznosov, 2020). With the
rise of e-sports and live-streaming, online game
players with excellent performance could gain fame
and sponsorship. This trend arouses some players’
vanity and further gives rise to another industry called
“MMR boosting” (Match Making Rating), which
means hiring someone to play their account to
improve their rank (Beserra, Camara, & Da Costa-
Abreu, 2016; League of Legends Support, 2022).
This involves many young people who are chasing
their careers of becoming professional e-sports
players offering this kind of service to provide for
themselves. Another common case is that some
agency websites are built to make it easier for the
clients to get customized services. The Riot games
company published an announcement in January
2022 banning one of its professional players from any
match because of participating in MMR boosting
(Riot games, 2022), and this is not a single case. The
prevalence of the MMR boosting service had push the
South Korean government to amend the law to punish
this kind of action (Milella, 2022). However,
technically there is not an effective way to identify
the massive account sharing actions caused by MMR
boosting.
Another study reported in (Matthews et al, 2016),
confirmed that passive sharing (e.g. accidental or
unsupervised sharing) did exist, but it is not the main
component of the sharing action, most of the sharing
actions were intentional. In fact, people had the
knowledge that sharing could endanger their privacy
and security, and they did the sharing after weighing
(Matthews et al.., 2016; Obada-Obieh et al., 2020).
Although the start of the sharing action could be
voluntary, the ending of account sharing might not be
as easy as it starts. People might not realize they have
reused the same password or similar passwords for
multiple accounts, and it has been found that with a
pre-known password, an attacker can successfully
predict the variant passwords in 41% of accounts in
under 3 seconds in an offline attack (Obada-Obieh et
al., 2020).
Moreover, since it is theoretically not legal for
two people to use the same game account, the
boundary and ownership of personal content are hard
to identify, which could lead to unexpected privacy
leakage and financial loss (Obada-Obieh et al., 2020).
2.2.2 User Authentication
Keyboard and mouse are the two essential
components of online gaming. In respect of safety
considerations, keystroke dynamics analysis is
inevitable to record users’ personal information
directly (e.g., account number, password, chat logs),
while mouse dynamics have less problem with this.
Moreover, the result from previous research on game
data has shown that the mouse movement data
contained more information gain than keystrokes
with respect to user identification and authentication
(Beserra et al., 2016).
Initially, Gamboa and Fred (2004) proposed
serials of features that could be used to define a mouse
movement in their research. In another study of
mouse movement curves reported in (Hinbarji,
Albatal, & Gurrin, 2015), nine features were defined
and extracted to characterize a single mouse action
which achieved an EER of 5.3%. The authors also
reported that with the increase of threshold, FRR
increases and FAR decreases respectively (Hinbarji,
Albatal, & Gurrin, 2015). A similar conclusion was
proposed in the Minecraft mouse movement study
(Siddiqui, Dave and Seliya, 2021), in which the
authors argued that they had achieved a lower FPR
with the cost of increased FNR, but this did not
include the effect of threshold changing. They also
delivered an opinion that, in practice, achieving
minimal FAR should be one of the priority tasks of a
user authentication system, since falsely accepting an
imposter as a true user could be more harmful than
falsely rejecting a true user (Siddiqui et al., 2021).
However, excessive FRR due to the pursuit of
minimal FAR could also cause a poor user
experience. Therefore, finding a balance between
these two values is important.
Another finding reported in (Hinbarji, Albatal, &
Gurrin, 2015), is that the authentication system can
achieve a lower EER in a lower threshold with a
longer session length, but a longer session length also