In areas such as CRM software and portals, open source gained a foothold because users were willing to compromise -- less could be more, because the price was right. In security, open source rushed in because commercial vendors fell down on the job. As security problems in the enterprise outstripped the capabilities of commercial solutions, a number of talented security researchers stepped into the breach via the open source model.

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From folks such as Renaud Deraison of Nessus to Martin Roesch of Snort, great security tools poured forth to the enterprise. There are now thriving open source security projects in anti-virus, anti-spam, personal and application firewalls, VPNs, IDS/IPS, wireless security, vulnerability assessment, and penetration testing to name but a few.

In network vulnerability assessment, our Bossie winner, Nessus, stands alone. The granddaddy of all security tools, Nessus combines an up-to-the-minute vulnerability engine and testing controls, making it an essential member of the toolbox in both well-funded and cash-strapped security organizations. It tests all aspects of a target including the operating system, ports, services, and applications, and it scores consistently as the top security tool based on professional security tester reviews. Reports can be lengthy, but they're comprehensive.

Nessus shows you where intruders might get in. Snort, which takes our Bossie for intrusion prevention, can stop them from doing so. Snort performs real-time traffic analysis and packet logging. In addition to classic protocol analysis, Snort now also performs content monitoring. Its rules language has evolved light-years beyond the version available when Snort was first released. And like Nessus, Snort is at the top of the heap in community support. The Snort project has spawned a range of add-on projects such as ACID (Analysis Console for Intrusion Databases), SnortSnarf, Swatch, and SnortCenter. These add-ons are needed for reporting and centralized control of multiple Snort boxes; Snort itself is strictly the detection and prevention engine.

In the case of anti-virus, one open source solution stands alone, ClamAV. ClamAV was recently purchased by Sourcefire, the owners of Snort. As with most projects on this distinguished list, ClamAV runs on Linux and Unix, and it was designed primarily for e-mail gateways. Virus signature updates are frequent and the detection engine is fast. ClamAV works well with Spamassassin within the MIMEDefang filtering framework for e-mail servers.

Our Bossie winner for anti-spam is the ubiquitous Spamassassin. Powerful, extensible, and effective, Spamassassin uses a trainable neural network engine to identify spam and minimize false positives, in addition to the classic techniques of blacklisting and Bayesian filtering.

Snatching our Bossie for best firewall is IPCop. IPCop is a complete Linux distribution with the sole purpose of network protection. Think of it as a Linux computer with one task: imposing security policies on network traffic. A competing project, SmoothWall, similarly turns any old PC into a high-functioning firewall appliance, but the Web management interface of IPCop is a bit more refined and thus edged out its competition.

Not to be outdone by the private sector, the exceptionally talented folks at the NSA created a superior application firewall called SELinux. The special sauce of this Linux distribution is a mandatory access control architecture for the OS kernel and major subsystems that keeps every process in check, ensuring that the action of one process cannot flow into another. Even the superuser is placed in isolation. A worthy competitor is Novell's open source AppArmor project, an easy-to-configure application firewall aimed exclusively at Suse distributions. SELinux continues to be better supported by the security community, and it forms the basis for a flexible security solution (versus a simple secure operating system). SELinux takes the Bossie.

OpenVPN, our Bossie winner for best SSL VPN, is the open source champion of secure connectivity. OpenVPN simply outshines its competition. It can be used to secure site to site links, remote access connections, and Wi-Fi networks, providing load balancing and fail-over capabilities. It runs on a wide range of operating systems and is supported by numerous open source projects and commercial products. And OpenVPN supports all ciphers and key sizes supported by OpenSSL, giving it tremendous flexibility.

Although not an application per se, the OSSTMM (Open Source Security Testing Methodologies Manual) is a phenom in the security world. The OSSTMM project provides an entire testing framework for security throughout the enterprise, including physical security, information security, Internet and wireless security, even security against fraud and social networking attacks. The OSSTMM provides a method for quantifying risk and an excellent foundation for security testing best practices. The project offers testing templates, intense community support, and a first-rate architect in Pete Herzog, scoring our Bossie for security testing best practices.

List of Bossie categories | Best of open source in software