1.1.1.3 Ensure mounting of squashfs filesystems is disabled - lsmod

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Information

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 system. If this filesystem type is not needed, disable it.

Impact:

As Snap packages utilizes squashfs as a compressed filesystem, disabling squashfs will cause Snap packages to fail.

Solution

Edit or create a file in the /etc/modprobe.d/ directory ending in .conf
Example: vim /etc/modprobe.d/squashfs.conf
and add the following line:

install squashfs /bin/true

Run the following command to unload the squashfs module:

# rmmod squashfs

See Also

https://workbench.cisecurity.org/files/3549