IT Baseline Protection Manual - Chapter 6.2 Unix network

6.2 Unix network

Description

Networked Unix systems consist of computers running on the Unix operating system and offering services (as servers) for other IT systems within a network, or making use of such services themselves (as clients).

In this chapter, the threats and safeguards described are specifically for Unix networks. Additional threats and safeguards applying to server-supported networks can be found in chapter 6.1.

Threat Scenario

The following typical threats (T) are assumed as regards IT baseline protection of a networked Unix system:

Organisational Shortcomings:

T 2.15 Loss of confidentiality of sensitive data in the Unix system
T 2.23 Security flaws involved in integrating DOS PCs into a server-based network

Human Failure:

T 3.10 Incorrect export of file systems under Unix
T 3.11 Improper configuration of sendmail

Technical Failure:

T 4.11 Lack of authentication possibilities between NIS Server and NIS Client
T 4.12 Lack of authentication possibilities between X Server and X Client

Deliberate Acts:

T 5.40 Monitoring rooms using computers equipped with microphones
T 5.41 Misuse of a Unix system with the help of uucp

Recommended Countermeasures (S)

For the implementation of IT baseline protection, selection of the required packages of safeguards ("modules") as described in chapters 2.3 and 2.4, is recommended.

In the following, the safeguard group "networked Unix system" is presented.

Some measures refer to the configuration of the various servers; other measures will have to be implemented by servers and clients in order to become effective. For any clients connected, the safeguards outlined in chapter 5 must be implemented.

6.2.1 Unix-Server

It is advisable to install the server in a separate server room. The appropriate measures are described in Chapter 4.3.2. If no server room is a available, a server cabinet should be used (c.f. Chapter 4.4).

In addition, the following measures will have to be taken:

Infrastructure:

S 1.28 (2) Local uninterruptable power supply (ups)

Organisation:

S 2.33 (2) Division of administrator roles under Unix

Hardware/Software:

Access to the Unix system

S 4.13 (1) Careful allocation of identifiers
S 4.14 (1) Mandatory password protection under Unix
S 4.18 (1) Administrative and technical means to control access to the system-monitor and single-user mode

Allocation of attributes / Working with the Unix system

S 4.9 (1) Use of the security mechanisms of X Windows
S 4.19 (1) Restrictive allocation of attributes for Unix system files and directories
S 4.20 (2) Restrictive allocation of attributes for Unix user files and directories
S 4.21 (1) Preventing unauthorised acquisition of administrator rights
S 4.22 (3) Prevention of loss of confidentiality of sensitive data in the Unix system
S 4.23 (3) Secure invocation of executable files

Logging / Security checks

S 4.25 (1) Use of logging in Unix systems
S 4.26 (2) Regular security checks of the Unix system
S 4.40 (2) Preventing unauthorised use of computer microphones
S 4.93 (1) Regular integrity checking

Communications:

S 5.16 (2) Survey of network services
S 5.17 (1) Use of NFS security mechanisms
S 5.18 (1) Use of NIS security mechanisms
S 5.19 (1) Use of the sendmail security mechanisms
S 5.20 (1) Use of the security mechanisms of rlogin, rsh and rcp
S 5.21 (1) Secure use of telnet, ftp, tftp and rexec
S 5.34 (2) Use of one-time passwords (optional)
S 5.35 (1) Use of uucp security mechanisms
S 5.36 (2) Encryption under Unix and Windows NT (optional)
S 5.38 (2) Secure integration of DOS PC's into a Unix network

Contingency Planning:

S 6.31 (2) Procedural patterns following a loss of system integrity
S 6.32 (1) Regular data backup

6.2.2 Unix-Client

To implement baseline protection into Unix security, the following measures must be implemented for each and every Unix client, along with the safeguards listed above which, in essence, apply to Unix servers.