A lot of focus has been on security in the open source industry lately, especially in the wake of the Heartbleed bug. This list includes a number of open source security tools anyone can use to improve the quality of their apps, desktop computers, network services, and more, and it includes software for penetration testing, malware analysis, IPv4 packet monitoring, computer forensics, and intrusion detection.
More from Network World (Note link goes to Reddit with a summary of the article)