A network firewall is a device or software that monitors and controls the incoming and outgoing network traffic based on predefined rules. A network firewall can help reduce the risk of denial of service (DoS) attacks, which are attempts to overwhelm a system or network with excessive requests or traffic, by filtering or blocking unwanted or malicious packets. A SQL injection attack is a type of code injection attack that exploits a vulnerability in a web application’s database query, by inserting malicious SQL statements into the input fields. A phishing attack is a type of social engineering attack that attempts to trick users into revealing sensitive information or installing malware, by sending fraudulent emails or messages that impersonate legitimate entities. An insider attack is a type of malicious activity that originates from within an organization, such as employees, contractors, or partners, who abuse their access privileges or credentials to compromise the confidentiality, integrity, or availability of information systems or data. A network firewall cannot prevent these types of attacks, as they rely on exploiting human or application weaknesses rather than network vulnerabilities.