Moreover, DFI and LEA are likely to have other ongoing
digital investigations. Their ongoing case commitments may
prevent them from being able to perform research on SCI
systems to identify the required evidence. Meanwhile, SCI
system owners may also be unable to provide the necessary
evidence since these requirements were not specified in the
first place when SCI was implemented. Caviglione et al.
[2] stressed that digital forensic investigation on IoT devices
would have to be performed on small-scale implementations
(such as homes) to large-scale deployments such as those
within a smart city. It was further stated that the technology
used to build the infrastructure would be diverse and that
their accessibility features must be discerned and appraised
independently for forensic investigations [2]. The predicament
has not gone unnoticed - there have been calls for further
digital forensic research on new digital artifacts and preventing
misinterpretations of artifacts [3].
Digital forensics and cybersecurity in smart cities had been
previously discussed, where the definition of smart cities
was based on National Institute of Standards and Technology
(NIST) and only focused on smart environments, living and
mobility [1]. While the threats, forensic data, and data sources
highlighted did provide some guidance for DFI and LEA [1],
the provided information cannot apply to all SCI internation-
ally. For example, different countries have different technical
requirements, implementation and data needs for their SCI.
This could prove problematic for solutions that suggest a one-
size-fits-all approach by specifically listing functional systems,
such as the ones suggested by Baig et al. [1].
Due to the complexity of SCI, digital evidence for various
components of SCI must be identified before actual cybercrime
occurs. This is to reduce the stress faced by DFI and LEA as
first responders to cybercrime. DFI and LEA could also better
handle SCI cybercrime challenges if a standard definition of
SCI is achieved, along with potential threats, offences and
evidence sources pre-identified. Although this is a global
challenge, adhering to global initiatives and standards allow
flexibility of adoption by international DFI and LEA.
The contributions of our research are summarized as fol-
lows:
1) We highlight current issues in SCI and define a standard-
ized definition of SCI.
2) We develop and make publicly available our threat model
template to governments, DFI and LEA to identify threats
in SCI.
3) We map SCI threats to possible offences and correspond-
ing SCI evidence sources and types.
4) We discuss future SCI digital forensics opportunities from
a technical and legal perspective.
For reproducibility and advancing the research in SCI
digital forensics and threat modeling, our threat model
is publicly available at: https://github.com/poppopretn/
SmartCityThreatModel.
The rest of this paper is organized as follows. In Section II,
we present the context of the paper and define SCI. In
Section III, we highlight the choice of our threat modeling
methodology, showcase our threat model and present the
threats identified in SCI. In Section IV, we show the threats,
offences, evidence sources and types within SCI that we
derived using our threat model. In Section V, we discuss future
technical and legal opportunities for SCI digital forensics. In
Section VI, we explain the limitations of our research. In
Section VII, we summarize current related work in SCI digital
forensics. Finally, we conclude the paper in Section VIII.
II. CONTEXTUALIZING SMART CITY INFRASTRUCTURE
Technological innovations and rapid deployment of Internet
of Things (IoT) devices have transformed many cities in
different geographical regions into smart cities [4]. Arguably,
these cities may not have implemented sufficient infrastructure
that can deliver futuristic societal outcomes such as accident-
free environments or zero-waste scenarios. However, these
current implementations have brought about positive changes
such as moulding the design of future cities and achieving
sustainable use of resources [4].
A. Current Issues in Smart City Infrastructure
The implementation of SCI is an attractive option for gov-
ernments looking to improve citizens’ lives and has increased
visibility to critical indicators such as resource utilization and
public safety. Nonetheless, there are multiple challenges to
implement such capabilities as outlined below:
1) Definition Issues: It is vital to set the right context and
definition when SCI is discussed. From the academic
perspective, a commonly agreed definition of a Smart
City has yet to be agreed on. A brief literature review
of papers regarding SCI was conducted and yielded at
least three different definitions of a Smart City [5]–[7].
SCI is not clearly defined from the industry perspective
either. Various industry solutions such as Bosch [8],
Cisco Kinetic for Cities [9], Microsoft CityNext [10]
and Schneider Electric EcoStruxure [11] have offered
products touted to allow prospective customers to create
smart cities. However, a review of their respective product
briefs showed that these solutions appear not to be based
on any commonly agreed upon definitions or standards.
Many also fail to realize that such forms of definition are
constrained by financial budgets and technological matu-
rity of the location SCI are deployed in. This inevitably
contributes to the problem of a lack of standard definition
in SCI.
2) Interoperability Issues: This is an extension of the
definition issue mentioned previously. There were at least
31 different vendors [12] offering various platforms and
technologies to build SCI. It is unlikely that any one
vendor could meet all the design requirements (hard-
ware and software) of a city/country. A more realistic
outcome would be a myriad of vendors being chosen
to implement technologies by their respective strengths.
With such a gamut of sensors, protocols, and tech-
nologies, interoperability between vendors becomes an
issue. Although entities such as FIWARE [13] and the
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