About a year ago, we took a look at the growing trend toward open-source security and highlighted 10 of the best apps available. Since then, the area has continued to mature, and now we're back highlighting 75 of the most frequently downloaded open-source security applications.

Open-source software vendor OpenLogic Inc. this week is unveiling a free software tool aimed at helping businesses look under the hood of their IT systems to find and inventory the open-source applications they're running.

Having many more eyes watching the code and a community of developers backing up users, open source security applications provide a wide range of options and made-to-order uses. Here's a list of 10 serious open source security applications, gathered via the word-of-mouth of the CSOs who use them.

To help developers audit Web application security, Google has released an open source tool called ratproxy. It is a non-disruptive tool designed for Web 2.0 and AJAX applications that produces an easy-to-read report of potential exploits.

A little over a year ago, we took a look at 10 Commercial Open Source Security Vendors. As we set out to update that list, two facts jumped out: 1) the number of open source security apps with commercial support has grown substantially and 2) the line between open source and commercial applications continues to blur.

For January and February, we chose some of the staples of open source security (GnuPG and Nmap) as the tool of the month. And deservedly so; both have just celebrated their ten-year anniversary in the open source realm, a rare feat for any open source project, much less one founded on security.

In this video recorded at Black Hat USA 2010, Patrick Thomas, a vulnerability researcher at Qualys, discusses the open source web application fingerprinting engine BlindElephant.

Two prominent open-source projects recently got a thumbs-up from Veracode, a company that applies a standards-based approach to software vulnerability testing.

Hewlett-Packard has launched the FOSSology Project, a tool for tracking and monitoring the use of free and open-source software within an IT environment.