The SG-CPS typically encompasses a multitude of interconnected systems that possess the capability to observe and manipulate tangible entities and ongoing operations. Like many networking systems, backdoors or loopholes in software or hardware may be accessed through the network to exploit the vulnerabilities of the entire system and launch cyber-attacks. Moreover, many technologies and applications of the SG that allow consumers and utilities to manage electricity consumption in response to supply conditions and electricity demands may increase the attack surface, i.e., more device and network technologies means that more vulnerabilities may exist. The trending research topics, applications, and technologies of the SG that increase complexity and heterogeneity are distributed energy resources (DER), smart meters, AMI, load shedding, load shifting, and demand response (DR).
3.2.2. SG Cyber-Physical Vulnerabilities: Communication Network
The network architecture of SG has been depicted in
Figure 6. To communicate, SGs employ both the HAN and the WAN. Each smart appliance in a home communicates with the SM across a home area network (HAN). Zigbee, Ethernet (wired or wireless), and Bluetooth are all methods of communication that the HAN can use to interact with other devices [
20]. Information interchange between heterogeneous devices in smart energy systems is enabled via a variety of communication topologies such as the home area network (HAN), neighbourhood area network (NAN), and wide area network (WAN). WLANs (wireless local area networks) such as Zigbee are important technologies for constructing a HAN network. Unfortunately, WLANs are susceptible to energy demand analysis and subsequent fraudulent message injection by unauthorized users. ZigBee is vulnerable to signal interference [
21]. WiMAX and LTE are implemented in NANs. WiMAX technologies are susceptible to radio-frequency link signal interference. LTE technology is also vulnerable to compromise if the evolved Node B (eNB) base stations are compromised, which allows access to all connected devices, including user equipment. The message exchange in a WAN may be susceptible to jamming that renders a particular PMU inaccessible and contributes to anomalous energy depletion at compromised nodes [
22]. In addition, the communication path between the PMU and the PDC is susceptible to replay and false injection assaults. The smart grid is subject to network-layer attacks. Ethernet-based communication in substation LANs, which is crucial for safety and control in digital substations, is susceptible to attacks that manipulate the operation of devices. Weak security rules in network device configurations can jeopardize smart grids at entrances and egresses where SCADA devices connect to the main network [
23]. IP packet tampering (source/destination address spoofing, fragmented message interruption, packet flag manipulation, and outstation data resetting) at network-layer devices such as routers and layer three switches also threatens the smart grid.
HANs use wireless communication through IoT technologies and protocols, allowing more devices, appliances, and protocols to be connected. Unfortunately, the security implemented in these devices is often incompatible. Additionally, the usage of external cloud providers to manage data volume and end-users prioritizing convenience over security are concerning developments in HANs [
24]. These variables increase the smart meter system’s attack surface, making HAN communications, including forecasting data, easier to intercept and change.
Wireless sensor networks (WSNs) and micro-electrical and mechanical technologies used in SG’s HANs and NANs gather and transmit data from the environment. WSN attacks, vulnerabilities, and security needs differ from wired network security because of sensor node limitations [
4]. Further, SG Cyber-physical vulnerabilities are found at the
protocol level, in the
IoT system, in
distributed energy resources, and in
advance metering infrastructures.
SG Cyber Vulnerabilities: Protocol Level Integrating Information and Communications Technology (ICT) in a smart grid is extensive and closely connected to the power infrastructure. When combined with a power system, a cyber system creates a full Cyber-Physical System (CPS). Various cyber vulnerabilities, accessed via vulnerable access points shown in
Figure 7, can pose security threats to the power system, leading to instability and unreliability of the CPS.
Information flows from the application to the HAN, NAN, and WAN. A secure application can be exploited at an insecure network protocol layer. Each form of the network has interdependent protocols. The SG comprises protocols from all four communication networks: Home, Local, and Wide Area Networks. TCP/IP, Ethernet, Modbus, DNP3, MQTT, OpenADR, OPC, and Wi-Max are popular SG network protocols. The various protocols have different standards, implementations, applications, and security. For example, due to their absence of authentication and permission, Modbus, IEC-60870-5-104, Profinet, and DNP3 pose cybersecurity risks [
25].
An SG inherits the cybersecurity weaknesses of its various technologies. Modbus is often used in industrial architectures because of its simplicity, e.g., it offers raw data transfer without authentication or encryption. However, these characteristics also make it vulnerable and easy to abuse [
26]. Many studies examined and detected the impact of various potential cyber-attacks on Modbus of the SG [
27,
28,
29]. Distributed network protocol version 3.0 (DNP3) is another critical infrastructure communication technology, especially in electrical installations. DNP3 was used in electrical stations to connect master stations (RTUs) and outstations (IEDs). An experiment was done to detect flaws and conduct penetration testing utilizing Man-in-the-middle (MITM) attacks on a simulated DNP3 system [
30]. Direct or indirect access to routers, switches, or hubs is often enough to attack a protocol. For example, to attach MQTT, Internet connectivity, or access to an ISP router is sufficient. A physically connected device like an RTU or control network can also attack Modbus or DNP3.
SG-CPS is similar to IoT systems, except CPS specifically stresses physical, networking, and computing activities. The Internet of Cyber-Physical Things (IoCPT) emerged from the use of IoT technologies in Cyber-Physical Systems (CPS) [
15]. The SG uses IoT to collect, monitor, and analyze electrical grid data and deliver control signals. It also uses cutting-edge technologies like Wireless Sensor Networks (WSNs), which can cause sinkhole, sybil, and wormhole cyberattacks. IoT’s reliance on the insecure internet creates major security issues. 2018 IEC 61850-8-2, an XMPP-based information mapping, was published to integrate SG and IoT, requiring WAN connectivity [
31].
Many reasons exist that make security in the IoT complex. Due to its lack of security, an IoT device is often the SG’s weakest link, allowing an enemy to enter the system and launch more attacks. Most IoT devices lack processing power or memory to encrypt data yet adhere to real-time constraints. Additionally, SG’s IoT device connection path is vulnerable to data theft, manipulation, and change due to a lack of secure protocols, public exposure, and oversight. IoT devices may interact with each other and their environment without human supervision, raising security and privacy concerns. Due to their interaction with many IoT devices, DAUs and PDCs with IoT capabilities are particularly vulnerable to network-level attacks. IoT device-level authentication is at risk due to public key implementation complexity and resource constraints. APIs might provide fake data injection vulnerabilities in SG visualization systems like the human-machine interface (HMI) without proper auditing. IoT-enabled SGs connect SMs, controllers, DAUs, PMUs, PDCs, and fault isolators to the Internet, enabling pervasive connection. Encrypted communication between DAUs, PDCs, and control centres is possible using the LoRaWAN IoT protocol [
32]. However, an attacker can enter the channel and change messages if the shared secret key is compromised.
Simple passwords are often not sufficient to protect IoT devices. Using spear-phishing, a 2015 Ukrainian power system cyberattack stole usernames and passwords from service provider network servers [
5]. The IoT/SCADA devices were connected remotely over VPNs using the credentials [
21]. Then, IoT/SCADA devices were remotely used to run malicious code to disrupt the system. Other attacks exploited IoT to access SG endpoints and interrupt power supply and generation. Many recent hacks are IoT-enabled, given the rapid usage of the Internet of Things. In [
33], writers examined recent, confirmed IoT-enabled attacks, including proof-of-concept and real-world cases.
The key thrusts for the economic and environmentally sustainable future are digitisation and decentralization of electricity grids. Distributed energy resources (DER) are becoming commonplace in power systems to achieve this goal. Examples of DER include electric vehicles, battery storage, rooftop solar panels, etc. DERs help power companies save money on operations while giving customers and aggregators more control over the energy they generate and utilize. The growth of distributed energy resources (DERs) has prompted interest in hybrid SG communications for monitoring and control. DER may provide whole distribution networks, enhancing the current electrical grid [
34].
DER can be used for various purposes. DER Energy may be used to lower costs and increase reliability. DER systems may improve local fuel efficiency and reduce pollution. DER technology can enhance electricity production and transmission and reduce distribution infrastructure and equipment needs. Additionally, local reliability and grid voltage may be improved via DER technologies. As the number of intermittent renewable energy sources (RES) increases, frequency and voltage will vary. The SG needs rapid, dependable communication and advanced sensing and protection technology to control and coordinate grid DERs.
The need for grid security rises with DER deployment.
Table 1 highlights the cyberattack vectors targeting DER assets. Due to DERs’ interconnectedness, interoperability, and support for remotely controllable features, cybersecurity is crucial [
35]. Furthermore, DER communication requirements and various DER designs exacerbate power systems’ cybersecurity issues.
DERs include communication links, cooperation, and remote control. Unexpected dynamic interactions that trip heavy transmission lines may disrupt regional electricity exports and imports. The authors in [
36] state that a cyberattack framework can cause undervoltage and overvoltage in a renewable energy smart distribution system. Top-level optimization problems allow attackers to develop optimal and suboptimal false data injection attack routes that may Undervoltage or overvoltage the system. The attackers can then target vulnerable system portions at optimal times [
37].
Analysis of communication protocol and device assaults shows significant differences in the functional level of attacks and targeted DER assets [
38]. Cyberattacks target process sensors, actuators, and controllers at levels 0 and 1 of the Purdue model [
18], whereas levels 3, 4, and 5 (communication, coordination, and control fabric) target DER systems. The min-max method presented in [
39] demonstrates the significance of cyberattacks on energy centers and DER. Although an attacker could raise costs via energy hub components, a method that enabled and disabled various components was used to reduce the hack’s economic impact.
Renewable energy sources (RESs) are rapidly entering the electrical grid due to declining reliance on traditional energy sources and increased power demand. Integrating renewable energy estimates with real-time SG system operations requires advanced IT. For example, attackers can alter wind and solar prediction data and send it to the control center to affect power scheduling, dispatch, real-time balancing, and reserve requirements. System abuse can occur when hackers change energy gain and reprogram wind turbines to reverse direction [
17]. Such attacks could damage wind farms and hinder system performance. Malware attacks increase as renewable cyber-physical power systems (CPPSs) replace traditional power grids due to cyber technology and RES use [
40]. On the other hand, a typical inverter-based power system within distributed energy resources (DERs) is more vulnerable to cyber attacks when it integrates with renewable energy. Specifically, false data injection attacks (FDIA) can cause cyber-physical switching attacks that can affect power converter components [
41].
The growth of sophisticated Advanced Metering Infrastructures has brought new security challenges to the SG. The SM receives messages from HAN devices and routes them to the appropriate service provider [
42]. The interactions between SMs’ communication endpoints pose serious safety issues. Santamarta’s work in [
43] suggests that SMs may include factory login account backdoors, giving users control over the power readings. Telnet transmits unencrypted data, which is another security flaw. When attackers seize control of SMs, harmful interactions with other devices or misleading data can cause power outages and poor decision-making. They may use the meter as a "bot" to target other networked computers. Billing information might be altered to lower power prices to show misleading information.
Additionally, AMI’s large-scale deployment makes it susceptible to many dangers, such as energy fraud, data theft, service outages, extortion, sabotage, terrorism, and hacktivism [
44,
45]. Malicious customers can hack home SMs and install malware to steal energy. Because the firmware was installed incorrectly, rogue nodes might send bogus data to DAUs, causing incorrect data collection. Energy corporations may use inaccurate data to make economic decisions [
46]. Hacked sensors of SM can be used to alter power pricing [
47].
Manipulating SM data at the end user’s location can cost the service provider and benefit the competitor [
19]. For example, the Puerto Rican Electric Power Authority lost
$400 million yearly because SM manipulated electrical usage data. The attacker may gain private home information by disaggregating SM data using pattern recognition and feature extraction. To mitigate these risks, measures must be developed to safeguard SM data confidentiality [
48].
3.2.3. SG Vulnerabilities in Load Management
For this survey’s purpose, we define a Load Management program to be implemented by a utility using SG capabilities to increase grid stability and reduce costs. The focus of research in this area has been on Demand Response, Load shedding, and Load shifting.
DR programs enable users to cut loads at peak demand to minimize SG energy consumption. Demand response is useful for smart grids because it may save costs and prevent load-related outages. These new computational advancements enabled by DR technology help SGs prevent blackouts and assist end-users and energy suppliers economically and environmentally. Energy systems require client interaction, making DR initiatives challenging. Energy cost, incentives, service satisfaction, and other variables affect consumer volunteerism.
An example DR program is depicted in
Figure 8. DR programs let utilities remotely disconnect client appliances or reduce peak power demand, relieving the system. When users enrol in the DR program, the service provider collects data directly from meters that measure aggregate kilowatt-hours (KWH) from heating, cooling, ventilation, lights, and plugged equipment. The supplier then alerts clients of projected DR occurrences, such as high-load periods, allowing them to reduce their load. The provider uses meter data during the DR event and projected behaviour to assess if the client reduced their load. Reduced loads are credited to consumers’ bills in the following payment cycle. DR promotes consumer engagement with incentives [
49]. Automatic Demand Response (ADR) consumers install smart devices that allow the utility to reduce their energy use automatically during high-demand periods without human involvement. While DR projects have focused on industrial complexes, researchers and professionals have also investigated home DR systems. Research indicates that demand response can support grid-interactive buildings with a high proportion of variable energy supplies and promote the use of renewable energy [
50,
51].
Demand bidding and stoppable DLC are incentive-based DR schemes. RTP, TOU, and CPP are billing mechanisms. These incentive-based DR schemes pay users to reduce energy consumption during high energy prices. In demand response (DR) programs that implement time-based pricing schemes, consumers change how they use energy during high demand in reaction to various tariffs [
52].
Pricing attacks and
energy theft assaults are the two most common forms of cyberattacks designed to interfere with DR programs [
53]. To attack power grids, attackers need only spread fake information to consumers about low electricity costs via the Internet or social media [
54,
55]. As a logical response to the incorrect information about low electricity prices, victims may increase their usage, possibly causing an abrupt load increase in the power grid. Then, the grid may experience an overload or peak load due to the unexpected spike in demand. Attackers committing energy theft assaults intentionally mislead utility companies about one or more consumers’ energy production or consumption for their financial gain or the utilities’ financial loss.
The authors in [
56] examined DR load scheduling cyberattacks. The study simulated denial of service (DoS) and phishing attacks on Home Energy Management Systems (HEMS) in (DR) to manipulate price and load profile data. Based on field data, this study [
57] shows how to identify anomalous and potentially malicious behaviour modifications as part of a cyber-physical intrusion detection mechanism. To evaluate DR situations, a test bed that simulates consumer behaviour and integrates hardware is proposed in [
58]. Researchers used this test bed to examine how attacks affect components, protocols, software, and perceived consumer behaviour.
The term shedding load refers to temporarily interrupting the electricity delivery at the point when the electricity demand is equivalent to supply. It is sometimes necessary to maintain the grid integrity by preventing the power grid from overloading. Load shedding, a form of load management, involves sporadically turning off the electricity or decreasing usage of primary sources until demand drops and more capacity becomes available.
As a critical CPS of the SG, the load-shedding scheme is subject to cyberattacks. [
59] investigates the detection of attacks under dynamic load-altering assaults (D-LAA) by attacking two weak loads concurrently. The second phase studies how dynamic load-altering assaults (D-LAA) rebuild cyber-physical systems (CPS).
The SG uses load shedding as an emergency management solution for high-frequency deviation and supply-demand mismatch. Since the SG system’s communication channels are easily hacked, attackers aim to disrupt the consensus approach of global information discovery. By creating an unknown input observer (UIO), a distributed load-shedding technique may detect and isolate misbehaving agents and prevent negative impacts [
60].
In [
61], the authors used a novel Reliable States WAUF LS (RSLS) approach to mitigate the vulnerability of Wide-Area Under-Frequency Load Shedding (WAUFLS) to avoid False Data Injection (FDI) cyberattacks. To protect the smart grid system from cyber attacks, utility companies can use a security game to study the impact of false data injection attacks on load shedding [
62].
In recent years, to operate and execute the utility program efficiently, prosumers (those who make and use energy) and demand response have gained popularity, notably in SG systems. Peak load shifting is essential for power system regulation as prosumers become more common [
63]. The load pattern depicts commercial, institutional, and residential energy consumption fluctuations. Demand Side Management (DSM) approaches can alter end-user load patterns in power distribution systems [
64]. DSM methods include filling gaps, reducing peaks, moving load, maintaining resources, adding new ones, and changing load shape.
Although load shifting in smart grids is beneficial for energy management and efficiency [
63,
64,
65,
66,
67,
68], it can also introduce vulnerabilities that malicious actors may exploit [
69]. Smart grids use modern technology, complex communication networks, and substantial data interchange to coordinate and regulate power use through load shifting. Load shifting components can be vulnerable to cyber-attacks, increasing system vulnerability [
70]. Unauthorized access to load-shifting communication infrastructure and control systems is a major risk. Hackers can acquire unauthorized control over load-shifting processes by exploiting weaknesses in system software, network protocols, or devices [
71]. They may alter load schedules, interrupt grid operations, and create widespread power outages by hacking these crucial components.
The smart grid ecosystem’s growing device connection and dependency creates another risk. Load shifting requires data communication between smart meters, sensors, and controls. An attacker with access to any of these devices might alter or introduce false data into the load-shifting process, causing faulty load forecasts or scheduling choices that destabilize the grid. Load shifting increases complexity and requires precise data and communication [
72]. Any data integrity or communication channel violation might affect load-shifting efficacy and dependability. Data tampering, communication protocol manipulation, and denial-of-service assaults can undermine scheduling algorithms and cause operational interruptions.