GKrellM is a GTK-based stacked monitor program that charts SMP CPUs, disks, load, active net interfaces, and internet connections. There are also builtin monitors for memory and swap, file systems with mount/umount feature, mailbox checking including POP3 and IMAP, clock/calendar, laptop battery, sensors (temperatures, voltages, and fans), and uptime. It has LEDs for the net monitors and an on/off button and online timer for PPP. There is a GUI popup for configuration, plugin extensions can be installed, and many themes are available. It also features a client/server monitoring capability.
Kismet is an 802.11 layer 2 wireless network detector, sniffer, and intrusion detection system. It will work with any wireless card which supports raw monitoring (rfmon) mode, and can sniff 802.11b, 802.11a, 802.11g, and 802.11n traffic (device drivers permitting). It identifies networks by passively collecting packets and detecting standard named networks, detecting (and given time, decloaking) hidden networks, and inferring the presence of non-beaconing networks via data traffic.
DansGuardian is a Web content filtering proxy that uses Squid to do all the fetching. It filters using multiple methods including, but not limited to, phrase matching, file extension matching, MIME type matching, PICS filtering, and URL/domain blocking. It has the ability to switch off filtering by certain criteria including username, domain name, source IP, etc. The configurable logging produces a log in an easy to read format. It has the option to only log text-based pages, thus significantly reducing redundant information (such as every image on a page).
downtimed is a program that monitors operating system downtime, uptime, shutdowns, and crashes and records such events. At OS startup it logs information about previous downtime. It then periodically updates a time stamp file on the disk, which is used to determine the approximate time when the system was last up and running. During a graceful system shutdown, it records a time stamp in another file. The downtimes(1) command line tool can be used to inspect records of past downtime.
ICPLD (Internet Connection Performance Logging Daemon) is a connection monitor that sends ICMP requests to IP addresses of your choice and monitors if your machine has a working network connection. It logs failed attempts to reach the hosts, and will stamp a log as soon as a reply is received. It keeps track of when and for how long the connection was unavailable and records both total down time and each occasion of interrupted connection. It supports IPv6 and can execute a command whenever a connection goes up or down, which is useful for alerting users.
trend is a general-purpose, efficient trend graph for "live" data. Data is read in ASCII format from a file or continuously from a FIFO, and is played in real-time into a multi-pass trend (much like a CRT oscilloscope or a strip chart). trend can be used as a rapid analysis tool for progressive or time-based data series together with trivial scripting.