3.1.4. Availability

Availability indicates that data, applications, and systems are available to end-users when they are required. Availability is compromised if someone pretends to be an authorized user to access the system and make the network busy [50]. Distributed denial of service (DDoS) is the most basic availability attack. In DDoS attacks, the incoming traffic is originated from multiple sources; therefore, making it difficult for offensive measures to identify a single malfunctioning device. A DDoS attack in IoT devices happens due to lack of security measures. The alternating direction method of multipliers [51] and honeypot game models [52] are used to protect the systems from DDoS attacks.

### *3.2. Cyber Attacks on Smart Homes*

In a HAN, various heterogeneous devices are connected to each other. The devices are interoperable and are managed remotely. An adversary is always searching to find an entry point to enter the network for different attacks.
