NSA Guidelines for Secure Linux Server Configuration

The US National Security Agency has published a new version of the 200-page manual (PDF) on the secure configuration of Red Hat Enterprise Linux 5. This is a very detailed manual that explains the principles of a secure system and in practice indicates all the necessary settings and a list of services that must be disabled ( This is one of the basic principles: minimize the amount of software).

There is also something like a cheat sheet on A4 sheet, which is also very convenient.

By the way, this is not the only guide from the NSA. Similar documents were drawn up for almost all operating systems :

Secure Mac OS X 10.6 Snow Leopard Configuration (October 2010)
Mac OS X 10.5 Leopard Secure Configuration (March 2009)
Using Software Restriction Policies (SRP) in Windows (March 2011)
Security Basics in Windows 7 (May 2011)
Windows Vista Security Guide (March 2009)
Plus documents on Windows Server 2008, Windows Server 2003, Windows XP, Solaris 10, Solaris 9. They have been publishing such reference books for many years, since the days of Windows 2000 and NT.
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The Red Hat Linux 5 manual is still at the top of the list, because it is on this system that numerous servers of the US government and special services work. This is a detailed document and it is updated regularly, the latest version 4.1 was released on February 28, 2011.

The level of paranoia in all NSA manuals is overwhelming, for example, they recommend turning off even audio ports on personal computers and deactivating cameras.

They also have a pretty useful switch configuration guide (PDF) that focuses on Cisco IOS, but the principles can be used in a different architecture.

Additionally:
Debian and Ubuntu Secure Configuration Guide