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.
Kernel Security Checker is a useful tool to locate attackers residing within a system by employing a direct analysis of the kernel through /dev/kmem and bypassing the hiding techniques of the intruder (kernel static recompilation or use of LKMs). It can find the modified syscalls from userspace, detect the promiscuous interfaces, and find the modifications applied to a protocol.
net-status-monitor is a simple console script to test whether Internet connectivity is working. If it is, the script tells you the external IP address (in case your dynamic DNS provider is down). If not, it tries to find the point where the connectivity fails. The output is quite simple, so you can put it on your grandmother's PC. "Just tell me what the read line says" should give you enough information.
Pantheios is a C/C++ logging API library. It offers an optimal combination of complete type-safety, very high efficiency, genericity, and extensibility. It is simple to use and extend, highly portable (platform and compiler independent), and it upholds the C tradition of only paying for what you use. Pantheios supports logging of message statements of arbitrary complexity, consisting of heterogenous types. Pantheios supports filtering of log messages based on severity level.
Nagstamon is a Nagios status monitor with a UI that resides in the systray or as a floating statusbar on your desktop. It informs you in realtime about the status of your Nagios, Icinga, Opsview, Ninja, Check_MK/Multisite, Centreon, or Thruk-monitored network. It alerts you with sound and visual notification. Failed hosts and services are easy to connect with by SSH, RDP, and VNC. Custom actions can be run on certain events. It works best with GNOME, but also with KDE, Mac OS X, and Windows.