Security Design Principles

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Nixu SNS
Security White Paper October 2006 Version 1.1


Nixu Software Limited Nixu Group
© Nixu Software Limited 2006. All Rights Reserved. 2
Contents
1 Security Design Principles.................................................................................................................... 3 1.1 Defense in Depth .......................................................................................................................... 4 1.2 Principle of Least Privilege............................................................................................................ 4 1.3 Principle of Default Deny .............................................................................................................. 4 2 Application Security.............................................................................................................................. 5 2.1 Software Components .................................................................................................................. 5 2.2 Authentication ............................................................................................................................... 5 2.3 Authorization and Access Controls............................................................................................... 6 2.4 Audit Trail ...................................................................................................................................... 6 2.5 Running Root-privileged Shell Commands .................................................................................. 7 3 O/S Security.......................................................................................................................................... 7 3.1 O/S Hardening .............................................................................................................................. 7 3.2 Firewall.......................................................................................................................................... 7 3.3 IPS................................................................................................................................................. 7 3.4 Patch Management....................................................................................................................... 7
© Nixu Software Limited 2006. All Rights Reserved. 3
1 Security Design Principles
This chapter describes some general security design principles used in Nixu SNS. Nixu SNS has been built on CentOS 4.3 operating system that has been specifically hardened for DNS use. CentOS is a freely distributable operating system built from the RHEL source available at: ftp://ftp.redhat.com/pub/redhat/linux/enterprise/4/en/os/i386/SRPMS. The system architecture of Nixu Secure Name Server (SNS) is depicted in Figure 1 below. Nixu SNS includes a web-based user-interface implemented using web server (Apache 2.0.52) and PHP-module (4.3.9). The environment has been hardened using Bastille hardening tool (version 3.0.9-1.0). For intrusion detection (IDS) and prevention (IPS), PSAD version1.4.6-1 has been used. The general functionality of the firewall and the IPS system is depicted in Figure 2 below.

Figure 1 Nixu SNS Architecture

Figure 2: IPS Architecture
© Nixu Software Limited 2006. All Rights Reserved. 4
1.1 Defense in Depth
Nixu SNS has been designed applying the Principle of Defense in Depth. Defense in Depth has been applied when more than one subsystem has to be compromised to compromise the security of the entire system. Defense in Depth is the concept of protecting a computer network with a series of defensive mechanisms such that if one mechanism fails, another will already be in place to block an attack.
In the case of Nixu SNS, the Principle of Defense in Depth involves the following:
. Encrypted connections . In-host firewall . IPS system . ACLs for enabled services . Services are running with secure configurations . Web-UI authenticates the users . Web UI writes logs of the user actions . O/S is hardened and backups are taken periodically . If possible, Perimeter firewall for the network is used... [download for more]