My friend Ozgur Yuksel answers about Oracle Enterprise Linux security:

- SELinux - http://www.nsa.gov/selinux/
- Netfilter IPtables - http://www.netfilter.org/
- Linux kernel auditing - http://people.redhat.com/sgrubb/audit/
- VPN/IPSec - http://ipsec-tools.sourceforge.net/
- TCP wrappers - ftp://ftp.porcupine.org/pub/security/index.html
- AIDE - http://www.cs.tut.fi/~rammer/aide.html
- RPM GPG signature as an IDS - http://rpm.org/
- GPG - http://gnupg.org/
- SSL - http://www.openssl.org/
- SSH - http://www.openssh.com/
- stunnel - http://www.stunnel.org/
- mod_ssl - http://www.modssl.org/
- nmap - http://nmap.org/
- tcpdump/libpcap - http://www.tcpdump.org/
- wireshark - http://www.wireshark.org/
- nss - http://www.mozilla.org/projects/security/pki/nss/
- Frequent/proactive kernel security updates from Unbreakable Linux Network - http://linux.oracle.com/
- Oracle Validated Configurations - http://www.oracle.com/technology/tech/linux/validated-configurations/ind...
- Open source - against HP-UX, AIX, Windows etc. - http://www.gnu.org/copyleft/gpl.html

NB. he puts "Open Source" as a Linux security feature ;-).