Free security tools are available on the Web for free that you should add to your toolbox. VMWare Server is available for free, patch management, QA, vulnerability remediation testing and other daily activities are now available without a significant capital investment. Iptables comes with most Linux distributions. Apache SpamAssassin: Fight Spam at the Gateway. Cheops-ng: “The Network Swiss Knife” is an excellent free way to map and monitor your network network systems.”]
Source: https://www.csoonline.com/article/2120835/the-cheapskate-s-infosecurity-toolbox.html