collectd is a small and modular daemon which collects system information periodically and provides means to store the values. Included in the distribution are numerous plug-ins for collecting CPU, disk, and memory usage, network interface and DNS traffic, network latency, database statistics, and much more. Custom statistics can easily be added in a number of ways, including execution of arbitrary programs and plug-ins written in Perl. Advanced features include a powerful network code to collect statistics for entire setups and SNMP integration to query network equipment.
Sshguard monitors services through their logging activity. It reacts to messages about dangerous activity by blocking the source address with the local firewall. Sshguard employs a clever parser that can transparently recognize several logging formats at once (syslog, syslog-ng, metalog, multilog, raw messages), and detects attacks for many services out of the box, including SSH, several ftpds, and dovecot. It can operate all the major firewalling systems, and features support for IPv6, whitelisting, suspension, and log message authentication.
Radiator RADIUS server is flexible, extensible, and authenticates from a huge range of authentication methods, including Wireless, TLS, TTLS, PEAP, SQL, proxy, DBM, files, LDAP, NIS+, password, NT SAM, Emerald, Platypus, Freeside, TACACS+, PAM, external, OPIE, POP3, EAP, MOTP, TOTP, HOTP, Active Directory, Vasco Digipass, SecurID, Yubikey, WiMAX, and many more. It runs on Unix, Linux, Solaris, Windows, MacOS 9, MacOS X, VMS, and more.
The Linux Virtual Server Project is a project to cluster many real servers together into a highly available, high-performance virtual server. The LVS load balancer handles connections from clients and passes them on the the real servers (so-called Layer 4 switching) and can virtualize almost any TCP or UDP service, like HTTP, HTTPS, NNTP, FTP, DNS, ssh, POP3, IMAP4, SMTP, etc. It is fully transparent to the client accessing the virtual service.
MoSShE (MOnitoring in Simple SHell Environment) is a simple, lightweight (both in size and system requirements) server monitoring package designed for secure and in-depth monitoring of a handful of typical/critical Internet systems. It supports email alerts and SLA monitoring out of the box, and whatever you can script. The system is programmed in plain (Bourne) SH, and made to be compatible with BASH and Busybox so it can easily be deployed on embedded systems. Monitoring is designed to be distributed over multiple systems, usually running locally. As no parameters are accepted from the outside, checks cannot be tampered or misused from outside. The system is designed to allow decentralized checks and evaluation as well as classical agent-based checks with centralized data accumulation. Agent data is transferred via HTTP, so available Web servers can be co-used for agent data transfer. Each agent creates simple (static) HTML pages with full and condensed status reports on each system, allowing simple local checks.
SmoothWall Express is a network firewall, designed with home and small business users in mind. It is based upon a security-hardened subset of the GNU/Linux operating system and is completely free to use, download, and distribute. SmoothWall Express offers facilities and features normally only seen in expensive commercial offerings.
Dante is a free implementation of the proxy protocols SOCKS version 4 and SOCKS version 5 (RFC 1928). It can be used as a firewall between networks, controlling outgoing traffic. The package consists of two parts: a socks server and a proxy client that supports socks, HTTP proxies, and UPnP. RFC 1961 (GSSAPI) is supported in both the client and the server. Commercial support is available.