Here are some applications and tools that can help you harden and tighten the security on your Linux or Unix box. Examples will follow for each application, tool or module in separate blog posts.
bastille System hardening. OS lock down program. Configures daemons, system settings and firewalls to be more secure.
tcpwrapper Add some security to your system with tcwrapper. /etc/hosts.allow and /etc/hosts.deny
samhain File integrity checks on the fly!
tripwire File integrity checks and much more.
SELinux Security-Enhanced Linux. Implements mandatory access control using Linux Security Modules in the Linux kernel. NSA started the development, and the project was later released to the open source community for further development.
Apparmor (Novell, SuSE). Discretionary access control (DAC) model by providing mandatory access control. (MAC)
iptables/netfilter
Packet filter for IPv4 and NAT. Packet filter rules in in the kernel.
The iptables command is for administration of the packet filtering rules and NAT. (Network Address Translation).
Andutteye
Monitor your systems in a most excellent way.
These are just a few of the security tools and programs out there, but if you master these, you will most
definitely have a more secure system or server.
