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.
Performance Co-Pilot (PCP) is a framework and set of services for supporting system-level performance monitoring and performance management. It provides a unifying abstraction for all of the interesting performance data in a system, and allows client applications to easily retrieve and process any subset of that data using a single API. A client-server architecture allows multiple clients to monitor the same host, and a single client to monitor multiple hosts. Archive logging and replay are integrated so that a client application can use the same API to process real-time data from a host or historical data from an archive.
Ettercap is a network sniffer/interceptor/logger for ethernet LANs. It supports active and passive dissection of many protocols (even ciphered ones, like SSH and HTTPS). Data injection in an established connection and filtering on the fly is also possible, keeping the connection synchronized. Many sniffing modes were implemented to give you a powerful and complete sniffing suite. Plugins are supported. It has the ability to check whether you are in a switched LAN or not, and to use OS fingerprints (active or passive) to let you know the geometry of the LAN.
OpenVPN is a robust and highly configurable VPN (Virtual Private Network) daemon which can be used to securely link two or more private networks using an encrypted tunnel over the Internet. OpenVPN's principal strengths include wide cross-platform portability, excellent stability, support for dynamic IP addresses and NAT, adaptive link compression, single TCP/UDP port usage, a modular design that offloads most crypto tasks to the OpenSSL library, and relatively easy installation that in most cases doesn't require a special kernel module.
bandwidthd tracks usage of TCP/IP network subnets and builds HTML files with graphs to display network utilization. Charts are built by individual IP to show their utilization over 2, 8, 45, and 400 day periods. It color codes HTTP, HTTPS, TCP,UDP, ICMP, VPN, and P2P traffic. Unlike MRTG, it tracks each individual IP address and subnets, not the status of any particular link. Static mode is fast and easy to set up and has few dependencies. Database mode supports filtering by subnet, multiple sensors, custom reports and intervals, and can process thousands of IPs efficiently. Network utilization can be logged in CDF or a backend database.
GNU VPE creates a virtual ethernet by creating host-to-host tunnels between multiple endpoints. Unlike other virtual private "network" solutions which merely create a single tunnel, it creates a real network with multiple endpoints. It is designed to be conceptually simple and straightforward to setup (assuming prior IP routing knowledge) without sacrificing flexibility. It is designed to sit on the gateway machines of company branches to connect them, but it can also be used to tunnel into a VPN with a variety of protocols (RAW IP, ICMP, UDP, TCP, HTTPS-Proxy, DNS).