Angel is a simple yet useful tool to monitor the services on your network. Technically speaking, it's a Perl program that runs every 'n' minutes (usually fired from your cron) and calls different perl subprograms (referred to as "plugins" from now on) to do the actual testing. It will then generate an HTML table containing the status of your network.
bcnu is a Web-based system management tool which delivers information on the status of networked systems in a simple and easy-to-use manner. It uses a web browser to display information about hosts in a tabular form. Historical information can be held indefinitely, and there is a powerful query tool available to interrogate it. Client systems can run an agent which logs information back to a central system. An agent scheduler is integrated to allow agents to be run at different intervals. Standard agents include ftp, http, disk space, logfiles, processes, and more.
changetrack is a program to monitor changes to files. If files are modified one day, and the machine starts working incorrectly some days later, changetrack can provide information on which files were modified, and help locate the problem. Changetrack will also allow recovery of the files from any stage.
Checkservice is a Perl script that monitors services on remote hosts. It uses plugins to provide a more thorough check than just a socket check, and can be configured to check multiple services on multiple hosts using two different methods (simple and extended). It is able to write logs and when running in the background enables warnings. It features a beep-, mail-, and SMS-warning system.
CHIRP is a tool for automating the creation of configuration trees for Cricket. It supports a plugin architecture for adding drivers which produce Cricket configuration files and supports automatic detection of device types. When a network device is identified, CHIRP dynamically associates a driver with it to produce the configuration file.
The ipaudit package records and displays network activity. It is useful for identifying heavy bandwidth users, intrusive telnet sessions, denial of service attacks, and scans. It includes ipaudit, which stores counts of bytes and packets for every combination of host/port pairs and protocol. The utilities total and ipstrings can be used to investigate network traffic records from the command line. ipaudit-web can collect network traffic statistics and generate Web reports.