## 2 Background
### Communication  
Communication is the process of transferring information from one place to another [22]. Every communication must consist of a sender, a message, and a receiver. The sender and receiver can be a person or a computerized device, whereas the message can be text, audio, video, voice, or other formats. Accuracy, effectiveness, security, and  
Figure 2: Working of a blockchain.  
the legitimate sender or receiver while bypassing the actual legitimate connection. This type of attack is used to steal information, to listen to conversations, and for spying. Session hijacking can be performed by sniffing the network, using a brute force attack (BFA), or using cross-site scripting (XSS) [26]. Session hijacking can be minimized in a network by using a secure socket shell (SSH), https (the secure mode of a website), or a complex session ID [27].  
Bots (originating from \"robot\") are software applications over the Internet working on automated tasks. A combination of bots can form a botnet, which can propagate and organize itself to compromise the system of communication. The bots have the ability to install worms that can harm the system by replicating themselves, and also install backdoors that can bypass the authentication and encryption in the system [28]. Bots also cause a denial of service (DoS), and its advanced form, a distributed denial of service (DDoS), which can take a network or system artificially offline. Such challenges and their remedies are discussed in [29]. In probing DNS caches, the IP address of the system accessing the network is checked in a local DNS server, and only IP addressed present in the local DNS server are allowed [30]. Malware (from \"malicious software\") is a computer program created with the intention of damaging a system or network. There are numerous types of malware, which are intended to have different behaviors; a list is provided in [31]. Data acquisition malware takes data from the victim; honeypots and spam-traps are existing examples. Anti-virus programs can detect data acquisition malware. Behavior monitoring malware aims to monitor changes in the system state and sends the collected data to the attacker, which can be utilized for malicious purposes. These types of malware are identified by  
Figure 3: Secure communication process.  
the server, and only permitting trusted computers to access the network. Port scanning regularly scans a system's ports to identify an open port for malicious purposes [35]. An open, compromised port can be catastrophic for any system, and can allow a hacker to access the system's data. This attack can be avoided by disabling the port scanning of the system. A Byzantine attack compromises mobile networks, and involves the hacking of one of the devices on the network due to the leakage of information or credentials, which allows that device to act as a legitimate device. This type of attack is very difficult to identify, but can be minimized by continuous monitoring of the behavior of every device on the network and blocking devices that act abnormally [36]. The threats to a network can be detected using specialized software [37], and incorporating techniques to detect malware, spyware, and other undesired applications on the network.