## 3 Background  
In this section, we provide background information regarding DR function. For more details, refer to [31; 32; 33; 34; 35; 36; 37; 38]. Power utility (PU) maintains two types of reserves, namely, regulating and contingency reserves [32]. The regulating reserve is used in response to regular load changes, whereas the contingency reserve is used in response to generation losses. Both reserves are composed of spinning and non-spinning reserves. The spinning reserve is the generation capacity that is synchronized to the power system and can be used without any further delay--for instance, load shedding via DR. The non-spinning reserve is an unattached capacity to the grid but can be made available in a specific period, such as in combustion turbines, or power storage units. The normal frequency range in the US \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Access**} & **Feedback** & **Attacks** & **Governor** & **Why?** \\ \hline \multirow{6}{*}{Directly} & & 1. Using botnet to turn on/off IoT & & Such devices change their functionality based on sensor data or state information. For instance, the thermostat does not turn off the heat \\  & Yes & vehicles, etc. [19; 26; 27; 28]. & Yes (local edge device) & if the temperature is below the value of X. A circuit breaker trips if the current is beyond a threshold value. \\  & & utility, an adversary controls circuit & & The governor can be used to enforce the security policy. \\ \hline \multirow{6}{*}{No} & & 3. Using botnet to turn on/off IoT & & Such devices do not take actions \\  & & devices such as microwaves, or other & & based on the state information. If \\  & & high wattage devices. [19] & & someone wants to use the microwave, the attacker turns on the microwave \\  & & 4. Using a cyber system in power & No & either via physical access or through a \\  & & utility, an adversary turns on/off & & mobile app remotely. The governor \\  & & storage units or Distributed Energy & & cannot be used to prevent attacks that \\  & & Resources (DRRs). & & control such devices maliciously. \\ \hline \multirow{6}{*}{In-directly} & & 5. Using a cyber system in power & & Functionality is implemented by a \\  & & utility or Demand Response & & Yes (where \\  & & Automation Server (DRAS), an adversary sends malicious signals to & commands are & information. For instance, DRAS \\  & & control Demand Response (DR) & issued) & sends load curtailment signals to \\  & & functionality [24]. & & customers to curtail load in response \\ \hline \multirow{6}{*}{Yes} & & 6. Using a cyber system in power & & to contingency. The governor enforces \\  & & utility, an adversary sends malicious & & the required and safety property to \\ \cline{1-1}  & & signals to the Automatic Generation & & commands that are issued by DRAS to \\ \cline{1-1}  & & Control (AGC) [30]. & & verify the need for those commands. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Attack scenarios where a governor might be useful. is 60 Hz. If a power utility is unable to supply power to meet peak demand, the grid's frequency will start decreasing. Moreover, if frequency crosses the under-protection threshold, the protection relays disconnect generators, and this may lead to cascading failures [39; 40]. DR is the smart grid technology that involves customers to adapt their electricity consumption from normal consumption patterns in response to contingencies. PU implements DRAS to perform DR functions in various areas. Each DRAS is assigned a set of zip codes and receives power consumption readings from those areas via aggregate load servers. PU and DRAS issue DR/AMI commands (see Figure 1) to perform load curtailment, send price signals, and control DER. PU responds when contingency occurs in an area and response needs to be taken in a different area. DRAS responds when a response needs to be taken in the same area during contingency. If DRAS is not able to mitigate the contingency, it requests PU to take action. Then, PU issues DR/AMI commands to DRAS of a different area.