Here are five of the best security programs available. They range from monitoring and sniffing to encryption. What makes a great security program? Fitness for purpose, effectiveness, reliability, and features. These programs have all these attributes, and much more than you might expect.
5. Nagios - While it's not a security program by definition, Nagios helps security by providing network monitoring, problem notification and management. Nagios has enterprise-class features, has been around for over 10 years, and has a large user base & support community. Nagios runs on Linux or Unix based operating systems. You can monitor Windows systems and other devices with it as well.
4. Wireshark - Wireshark is an excellent tool for sniffing and capturing network traffic, as well as examining protocols and sessions in depth. Whether you need to capture wireless Ethernet traffic, or examine specific session content, this is an indispensable tool. Wireshark runs on many platforms, and supports many capture file formats.
3. Snort - Snort is a free, open source intrusion detection and prevention system (IDS/IPS). It can also function as a sniffer and packet logger. Real time alerts and analysis are possible with Snort as well. It is a high performance IDS that supports logging to many different databases, and can run on Unix based operating systems as well as Windows.
2. Nessus - Nessus is a powerful vulnerability scanner, due to its speed, accuracy, and depth. Nessus has over 28K plugins available and supports automatic updates for new plugins. Nessus 4 is one of the fastest scanners out there and is very flexible. You can get started with Nessus for free, which is another great thing about it.
1. Stunnel - Stunnel is a versatile tool that allows you to encrypt any TCP connection using an SSL wrapper. It is designed for if you have a service or daemon that is not Secure Sockets Layer (SSL) capable but you need to encrypt the sessions. Stunnel does require an SSL library in order to function, such as OpenSSL.
You say, "Clemmer, I've heard of these before, mainly from your own articles!" Well then, consider yourself well-informed. I mention these tools frequently because they are the best, because I've used them myself, and because I believe they will work for you. While this is a short list, with these tools you have a strong foundation to build on. Give the ones you haven't heard of a try. Another reason they are great is that they are all free.