cis-ubuntu1204-v110-4-2

name	cis-ubuntu1204-v110-4-2
description	Enable XD/NX Support on 32-bit x86 Systems
category	cis-os-hardening
version	1.1.0
author	cyberstrike-official
tags	["cis","ubuntu",12.04,"linux","process-hardening","nx","xd","buffer-overflow","memory-protection"]
cis_id	4.2
cis_benchmark	CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

4.2 Enable XD/NX Support on 32-bit x86 Systems (Not Scored)

Profile Applicability

• Level 1

Description

Recent processors in the x86 family support the ability to prevent code execution on a per memory page basis. Generically and on AMD processors, this ability is called No Execute (NX), while on Intel processors it is called Execute Disable (XD). This ability can help prevent exploitation of buffer overflow vulnerabilities and should be activated whenever possible. Extra steps must be taken to ensure that this protection is enabled, particularly on 32-bit x86 systems. Other processors, such as Itanium and POWER, have included such support since inception and the standard kernel for those platforms supports the feature.

Rationale

Enabling any feature that can protect against buffer overflow attacks enhances the security of the system.

Audit Procedure

Using Command Line

Run the following to see if your kernel has identified and activated NX/XD protection:

dmesg | grep NX

Expected Result

The output should contain: NX (Execute Disable) protection: active

Remediation

Using Command Line

On 32-bit systems install a kernel with PAE support, no installation is required on 64-bit systems:

If necessary configure your bootloader to load the new kernel and reboot the system.

You may need to enable NX or XD support in your BIOS.

Default Value

On 64-bit systems, NX/XD protection is enabled by default. On 32-bit systems, a PAE-enabled kernel may be required.

References

• CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0

Profile

Level 1 - Not Scored