MailScanner is an email virus scanner, vulnerability protector, and spam tagger. It supports the Postfix, Sendmail, Exim, Qmail, and ZMailer MTAs, and the Sophos, McAfee, F-Prot, F-Secure, CommandAV, InoculateIT, Inoculan, eTrust, Kaspersky, Nod32, AntiVir, BitDefender, RAV, Panda, DrWeb, ClamAV, and other anti-virus scanners. It uses SpamAssassin for highly successful spam identification, and is designed to handle denial of service attacks. It will detect password-protected zip files and apply filename checking to their contents. It is very easy to install, requires no changes at all to your sendmail.cf file, is designed to be lightweight, and won't grind your mail system to a halt with its load. It can be integrated into any email system, regardless of the software in use.
Arno's IPTABLES Firewall Script is a secure stateful firewall for both single and multi-homed machines. It supports NAT and SNAT, port forwarding, ADSL ethernet modems with both static and dynamically assigned IPs, MAC address filtering, stealth port scan detection, DMZ support, protection against SYN/ICMP flooding, experimental IPv6 support, multi-interface/aliased-IP support, and extensive user definable logging with rate limiting to prevent log flooding. It has plugin support to add extra features (like SSH Brute Force protection and (Racoon) IPSEC support). It is easy to configure and highly customizable. A filter script that makes your firewall log more readable is also included.
FireHOL a simple yet powerful way to configure stateful iptables firewalls. It can be used for almost any purpose, including control of any number of internal/external/virtual interfaces, control of any combination of routed traffic, setting up DMZ routers and servers, and all kinds of NAT. It provides strong protection (flooding, spoofing, etc.), transparent caches, source MAC verification, blacklists, whitelists, and more. Its goal is to be completely abstracted and powerful but also easy to use, audit, and understand.
AMaViS (A Mail Virus Scanner) scans e-mail attachments for viruses using third-party virus scanners available for UNIX environments. It resides on a UNIX (Linux) machine and looks through the attached files arriving via e-mail, generates reports when a virus is found and sets the delivery on hold.
Heartbeat is a full-function high-availability system for Linux and other POSIX-like OSes. It monitors services and restarts them on errors. When managing a cluster (more than 1 machine), it will also monitor the members of the cluster and begin recovery of lost services in less than a second. It runs over serial ports and UDP broadcast/multicast, as well as OpenAIS multicast. It is easily adapted to different interconnect media and protocols. When used in a cluster, it can operate using shared disks, data replication, or no data sharing. Versions starting with 2.0 are comparable to any commercial HA package, providing resource monitoring, larger clusters, and detailed dependency information.
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.