The /tmp directory is a world-writable directory used for temporary file storage. Ensure it has its own partition or logical volume at installation time, or migrate it using LVM.

The /var directory is used by daemons and other system services to store frequently-changing data. Ensure that /var has its own partition or logical volume at installation time, or migrate it using LVM.

System logs are stored in the /var/log directory. Ensure that it has its own partition or logical volume at installation time, or migrate it using LVM.

Audit logs are stored in the /var/log/audit directory. Ensure that it has its own partition or logical volume at installation time, or migrate it later using LVM. Make absolutely certain that it is large enough to store all audit logs that will be created by the auditing daemon.

If user home directories will be stored locally, create a separate partition for /home at installation time (or migrate it later using LVM). If /home will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later.

To ensure the system can cryptographically verify base software packages come from Red Hat (and to connect to the Red Hat Network to receive them), the Red Hat GPG key must properly be installed. To install the Red Hat GPG key, run:

$ sudo rhn_register

$ sudo rpm --import /media/cdrom/RPM-GPG-KEY

To ensure signature checking is not disabled for any repos, remove any lines from files in /etc/yum.repos.d of the form:

gpgcheck=0

Install the AIDE package with the command:

$ sudo yum install aide

The RPM package management system can check file access permissions of installed software packages, including many that are important to system security. After locating a file with incorrect permissions, run the following command to determine which package owns it:

$ rpm -qf FILENAME

$ sudo rpm --setperms PACKAGENAME

The nodev mount option prevents files from being interpreted as character or block devices. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of any non-root local partitions.

The nodev mount option prevents files from being interpreted as character or block devices. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions.

The noexec mount option prevents the direct execution of binaries on the mounted filesystem. Preventing the direct execution of binaries from removable media (such as a USB key) provides a defense against malicious software that may be present on such untrusted media. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions.

The nosuid mount option prevents set-user-identifier (SUID) and set-group-identifier (SGID) permissions from taking effect. These permissions allow users to execute binaries with the same permissions as the owner and group of the file respectively. Users should not be allowed to introduce SUID and SGID files into the system via partitions mounted from removeable media. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions.

The nodev mount option can be used to prevent device files from being created in /tmp. Legitimate character and block devices should not exist within temporary directories like /tmp. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /tmp.

The noexec mount option can be used to prevent binaries from being executed out of /tmp. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /tmp.

The nosuid mount option can be used to prevent execution of setuid programs in /tmp. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /tmp.

The nodev mount option can be used to prevent creation of device files in /dev/shm. Legitimate character and block devices should not exist within temporary directories like /dev/shm. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm.

The noexec mount option can be used to prevent binaries from being executed out of /dev/shm. It can be dangerous to allow the execution of binaries from world-writable temporary storage directories such as /dev/shm. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm.

The nosuid mount option can be used to prevent execution of setuid programs in /dev/shm. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm.

The /var/tmp directory is a world-writable directory. Bind-mount it to /tmp in order to consolidate temporary storage into one location protected by the same techniques as /tmp. To do so, edit /etc/fstab and add the following line:

/tmp     /var/tmp     none     rw,nodev,noexec,nosuid,bind     0 0

To configure the system to prevent the cramfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install cramfs /bin/false This effectively prevents usage of this uncommon filesystem.

To configure the system to prevent the freevxfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install freevxfs /bin/false This effectively prevents usage of this uncommon filesystem.

To configure the system to prevent the jffs2 kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install jffs2 /bin/false This effectively prevents usage of this uncommon filesystem.

To configure the system to prevent the hfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install hfs /bin/false This effectively prevents usage of this uncommon filesystem.

To configure the system to prevent the hfsplus kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install hfsplus /bin/false This effectively prevents usage of this uncommon filesystem.

To configure the system to prevent the squashfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install squashfs /bin/false This effectively prevents usage of this uncommon filesystem.

To configure the system to prevent the udf kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d: install udf /bin/false This effectively prevents usage of this uncommon filesystem.

The SGID (set group id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SGID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SGID files.

The file /etc/init.d/functions includes initialization parameters for most or all daemons started at boot time. The default umask of 022 prevents creation of group- or world-writable files. To set the default umask for daemons, edit the following line, inserting 022 or 027 for umask appropriately:

umask 027

To disable core dumps for all users, add the following line to /etc/security/limits.conf:

*     hard   core    0

To set the runtime status of the fs.suid_dumpable kernel parameter, run the following command: # sysctl -w fs.suid_dumpable=0 If this is not the system's default value, add the following line to /etc/sysctl.conf: fs.suid_dumpable = 0

To set the runtime status of the kernel.exec-shield kernel parameter, run the following command: # sysctl -w kernel.exec-shield=1 If this is not the system's default value, add the following line to /etc/sysctl.conf: kernel.exec-shield = 1

To set the runtime status of the kernel.randomize_va_space kernel parameter, run the following command: # sysctl -w kernel.randomize_va_space=2 If this is not the system's default value, add the following line to /etc/sysctl.conf: kernel.randomize_va_space = 2