A log analyser for MTA logfiles (for example sendmail). (C++) [GNU/Linux, Unix]

A web server logfile analyzer that works as a CGI and/or from command line, and supports multiple languages. (Perl)

Parses the logfiles of a wide variety of Web proxy servers and generates reports. (Perl) [Linux, Unix]

Resolves IP numbers to hostnames like in Apache, Squid, or other logfiles. It is able to cache lookups in a file. (Perl)

A general purpose monitoring engine for use by home users and system administrators (Perl) [Unix, Win32]

Emails a report of all packets that have been logged by the kernel's ipchains or iptables packet filtering subsystems. (Perl) [GNU/Linux]

Web page checker based on regular expressions. (Java) [Linux, Windows]

A tool to measure the maximum TCP bandwidth between two points on the internet. (C++) [Many platforms]

A network load monitoring applet for GNOME. (C) [GNU/Linux, FreeBSD]

An active network monitor with plugins to monitor several types of services, e.g. ftp, http, tcp port, disk space. (C) [GNU/Linux, Unix]

Ngrep is a pcap-aware tool that will allow you to specify extended regular expressions to match against data part of packets on the network. (C) [GNU/Linux, BSD, Windows 95/98/2000]

A network interface traffic statistics reporting and graphing tool. (PHP)

A tool that shows the network usage. It can be used interactively, or in web mode. (C) [GNU/Linux, Unix, Windows]

A network monitoring tool that represents network information via audio output, so that you can hear whether the network as a whole sounds normal. (C, Perl) [GNU/Linux, SunOS/Solaris]

Assists in visualizing a Data Center's computer rack layouts by creating a web page with HTML tables to show a frontview of the racks. Included are brief commandline and CGI scripts to demonstrate its implementation. (Perl) [Linux]

RUE is a monitoring/profiling tool for any Java based server. (Java)

Perl script which parses for attacks a squid log file. Allows to run commands or automatically notify the attacker's ISP upon trigger.

Software for application and network monitoring - logging, monitoring, capacity planning, availability and performance measurement, and helpdesk information. (C, PHP) [POSIX]