metadata/service/system/cis/cis-1-1-1-6.yml

# 1.1.1.6 Ensure mounting of squashfs filesystems is disabled
#
# Description
# ===========
# The squashfs filesystem type is a compressed read-only Linux filesystem
# embedded in small footprint systems (similar to cramfs). A squashfs image
# can be used without having to first decompress the image.
#
# Rationale
# =========
# Removing support for unneeded filesystem types reduces the local attack
# surface of the server. If this filesystem type is not needed, disable it.
#
# Audit
# =====
# Run the following commands and verify the output is as indicated:
#
#   # modprobe -n -v squashfs
#   install /bin/true
#   # lsmod | grep squashfs
#   <No output>
#
# Remediation
# ===========
# Edit or create the file /etc/modprobe.d/CIS.conf and add the following line:
#
#   install squashfs /bin/true
#
# NOTE
# ====
# In Ubuntu 16.04 squashfs is built into kernel, and 'install' command
# from modprobe.d dir has no effect. However, this is still checked by
# CIS-CAT in Ubuntu 16.04 benchmark v.1.0.0. This was removed in v.1.1.0.
#
parameters:
  linux:
    system:
      kernel:
        module:
          squashfs:
            install:
              command: /bin/true