A software firewall is a program that monitors and controls the incoming and outgoing network traffic on a computer or a server. A software firewall can help prevent unauthorized LAN devices from accessing stored files on a company file server by applying rules and policies that filter the network packets based on their source, destination, protocol, port, or content. A software firewall can also block or allow specific applications or services from communicating with the network, and alert the administrator of any suspicious or malicious activity12.

A software firewall is a better option than the other choices because:

Password complexity (B) is a good practice to protect the file server from unauthorized access, but it is not sufficient by itself. Password complexity refers to the use of strong passwords that are hard to guess or crack by attackers, and that are changed frequently and securely. Password complexity can prevent brute force attacks or credential theft, but it cannot stop network attacks that exploit vulnerabilities in the file server software or hardware, or that bypass the authentication process34.

Antivirus application © and anti-malware scans (D) are important tools to protect the file server from viruses and malware that can infect, damage, or encrypt the stored files. However, they are not effective in preventing unauthorized LAN devices from accessing the files in the first place. Antivirus and anti-malware tools can only detect and remove known threats, and they may not be able to stop zero-day attacks or advanced persistent threats that can evade or disable them. Moreover, antivirus and anti-malware tools cannot control the network traffic or the file server permissions, and they may not be compatible with all file server platforms or configurations56.