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Showing SKILL.md
| name | cis-ubuntu1804-v220-1-1-1-2 |
| description | Ensure mounting of freevxfs filesystems is disabled |
| category | cis-storage |
| version | 2.2.0 |
| author | cyberstrike-official |
| tags | ["cis","ubuntu","linux","ubuntu-18.04","filesystem","freevxfs","kernel-module"] |
| cis_id | 1.1.1.2 |
| cis_benchmark | CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 |
| tech_stack | ["ubuntu","linux"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | {} |
Level 1 - Server / Level 1 - Workstation, Assessment: Automated
The freevxfs filesystem type is a free version of the Veritas type filesystem. This is the primary filesystem type for HP-UX operating systems.
Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it.
None noted.
Run the following script to verify the freevxfs module is disabled:
#!/usr/bin/env bash
{
l_output="" l_output2="" l_output3="" l_dl=""
l_mname="freevxfs"
l_mtype="fs"
l_searchloc="/lib/modprobe.d/*.conf /usr/local/lib/modprobe.d/*.conf /run/modprobe.d/*.conf /etc/modprobe.d/*.conf"
l_mpath="/lib/modules/**/kernel/$l_mtype"
l_mpname="$(tr '-' ' ' <<< "$l_mname")"
l_mndir="$(tr '-' '/' <<< "$l_mname")"
module_loadable_chk()
{
l_loadable="$(modprobe -n -v "$l_mname")"
[ "$(wc -l <<< "$l_loadable")" -gt "1" ] && l_loadable="$(grep -P -- "(^\h*install|\b$l_mname)\b" <<< "$l_loadable")"
if grep -Pq -- '^\h*install \/bin\/(true|false)' <<< "";
l_output=
l_output2=
}
()
{
! lsmod | grep > /dev/null 2>&1;
l_output=
l_output2=
}
()
{
l_dl=
modprobe --showconfig | grep -Pq -- ;
l_output=
l_output2=
}
l_mdir ;
[ -d ] && [ -n ];
l_output3=
[ != ] && module_deny_chk
[ = ];
module_loadable_chk
module_loaded_chk
l_output=
[ -n ] && -e
[ -z ];
-e
-e
[ -n ] && -e
}
Run the following script to disable the freevxfs module:
If the module is available in the running kernel:
install freevxfs /bin/false in the /etc/modprobe.d/ directoryblacklist freevxfs in the /etc/modprobe.d/ directoryIf available in ANY installed kernel:
blacklist freevxfs in the /etc/modprobe.d/ directoryIf the kernel module is not available on the system or pre-compiled into the kernel:
#!/usr/bin/env bash
{
l_mname="freevxfs"
l_mtype="fs"
l_mpath="/lib/modules/**/kernel/$l_mtype"
l_mpname="$(tr '-' ' ' <<< "$l_mname")"
l_mndir="$(tr '-' '/' <<< "$l_mname")"
module_loadable_fix()
{
l_loadable="$(modprobe -n -v "$l_mname")"
[ "$(wc -l <<< "$l_loadable")" -gt "1" ] && l_loadable="$(grep -P -- "(^\h*install|\b$l_mname)\b" <<< "$l_loadable")"
if ! grep -Pq -- '^\h*install \/bin\/(true|false)' <<< "$l_loadable"; then
echo -e "\n - setting module: \"$l_mname\" to be not loadable"
echo -e "install $l_mname /bin/false" >> /etc/modprobe.d/"$l_mpname".conf
fi
}
module_loaded_fix()
{
if lsmod | grep "$l_mname" > /dev/null 2>&1; then
echo -e "\n - unloading module \"$l_mname\""
modprobe -r "$l_mname"
fi
}
module_deny_fix()
{
if ! modprobe --showconfig | grep -Pq -- "^\h*blacklist\h+$l_mpname\b"; then
echo -e "\n - deny listing \"$l_mname\""
echo -e "blacklist $l_mname" >> /etc/modprobe.d/"$l_mpname".conf
fi
}
for l_mdir in $l_mpath; do
if [ -d "$l_mdir/$l_mndir" ] && [ -n "$(ls -A $l_mdir/$l_mndir)" ]; then
echo -e "\n - module: \"$l_mname\" exists in \"$l_mdir\"\n - checking if disabled..."
module_deny_fix
if [ "$l_mdir" = "/lib/modules/$(uname -r)/kernel/$l_mtype" ]; then
module_loadable_fix
module_loaded_fix
fi
else
echo -e "\n - module: \"$l_mname\" doesn't exist in \"$l_mdir\"\n"
fi
done
echo -e "\n - remediation of module: \"$l_mname\" complete\n"
}
Not disabled by default.
v8 - 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software (IG 2, IG 3) v7 - 9.2 Ensure Only Approved Ports, Protocols and Services Are Running (IG 2, IG 3)
MITRE ATT&CK Mappings: T1005, T1005.000 (TA0005) - M1050