# A Systematic Literature Review on Penetration Testing in Networks: Future Research Directions
## 1 Introduction  
We currently live in the age of technology, which is integrated into our daily lives and is based on the internet. Technology makes it easy for its users to perform activities online. Although technology offers many conveniences and opportunities, it has some risks such as cyber attacks. These risks are due to aggressive competition between commercial and non-commercial organizations that use networks to deliver services. In order to deliver services, we need open ports in networks. A TCP or UDP port number that is open accepts packets, while a closed port denies connections or ignores all communication. Ports are used for all internet communications. Consequently, certain ports are required for internet-based services to receive and transmit data. If the service listening on the port is misconfigured, unpatched, vulnerable to attack, or has inadequate network security controls, open ports can pose a risk and are referred to as vulnerable ports [1]. We have found that it is easy to exploit any vulnerabilities in order to implement any type of attack. Therefore, many individuals and organizations are affected by this attack, which leads to the shutdown of individuals' networks and organizations' websites. For example, around 500 Coop supermarkets in Sweden had to close in 2021. The reason for this was because of a ransomware hack that hit businesses around the world. Late Sunday, the hackers demanded USD 70 million to release the encrypted files the ransomware washolding. Coop did not respond and their payment service provider was obliged to manually restore the payment terminals in each store using backups to fix the problems [2]. To prevent these attacks, organizations use tests called penetration tests. These are referred to as ethical hacking and white hat attacks. Penetration testing is a method of identifying security vulnerabilities in networks, applications, and computer systems that can be exploited by attackers. Penetration testing is a proactive way to identify vulnerabilities in digital assets by actively looking for vulnerabilities and exploiting them from the attacker's perspective. To achieve the cyber security objectives, which are integrity, availability, and confidentiality in the modern digital environment, penetration testing has become a mandatory element, especially with the introduction of the European General Data Protection Regulation for institutions and enterprises. Today, there are varieties of options for penetration testing. There are a variety of systems with tools that perform penetration testing including Kali Linux with such security tools as Nmap. Penetration tests are used to detect the vulnerabilities present in the system and to know how to eliminate them. They simulate different types of attacks on the target system. Through these tests, the tester can identify the vulnerabilities in an organized and controlled manner. Thus, they create reports of the problems requiring system repair and patch security vulnerabilities to the management. This is considered to be a risk assessment and can be used to verify network security. Penetration testing is very important for organizations but the resources are costly and time consuming. Therefore, a specialized penetration testing technique is needed to protect systems and devices and to ensure information and network security in a fast and inexpensive way. The use of the internet has become widespread. Therefore, data security is very important to prevent the attempts of cyber criminals. Prior to the criminals' attempt to exploit the vulnerabilities in a network, the specialists will have conducted penetration tests to detect and fix the vulnerabilities. A network can be an IoT network, LAN, WLAN, or WAN. The network penetration test is an ethical precaution designed to identify the risks that may occur if an attacker gains access to the company's computer systems and networks.