Lynis is an auditing and hardening tool for Unix derivatives like Linux/BSD/Solaris. It scans systems to detect software and security issues. Besides security-related information, it will also scan for general system information, installed packages, and possible configuration mistakes. The software is aimed at assisting automated auditing, software patch management, and vulnerability and malware scanning of Unix-based systems.
The RegLookup project is devoted to direct analysis of Windows NT-based registry files. RegLookup provides command line tools, a C API, and a Python module for accessing registry data structures. The project has a focus on providing tools for digital forensic examiners (though it is useful for many purposes), and includes algorithms for retrieving deleted data structures from registry hives.
Bartlby is a network and system monitor, completely written in C, to provide a scalable framework with the ability to monitor networks of various sizes. It consists of a core daemon, several plugins, and a Web GUI (PHP extension). The core daemon checks (over active/passive TCP) services/hosts and notifies users in case of critical service conditions (mail, SMS, ICQ, and custom triggers are supported). Bartlby provides an open plugin interface to give every administrator an easy to use option to extend the plugin base, and a fully customizable GUI (written in PHP using a C extension). Nearby everything can be controlled via an XML interface.
UnusedPkg is a diagnostic tool to search the oldest unused packages in your Linux system. UnusedPkg prints a sorted list with the size and number of days that a package has been idle. This helps you determine what packages can be manually removed to clean the system. It supports any apt-based distribution (tested on Debian and Ubuntu) and Slackware.
CaiCai is a network and services monitoring system. It performs tests for ping, DHCP, POP3, SMTP, FTP, etc. It does not require additional software installed on the remote side. It is fully configurable. It provides instant reports (via an HTML page), logs, statistics, and sound alarms.