cis-ubuntu2004-v300-3-1-2

DevOps & Security

Ensure wireless interfaces are not available

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_20.04_LTS_Benchmark_v3.0.0/cis-ubuntu2004-v300-3-1-2/SKILL.md

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3.1.2 Ensure wireless interfaces are not available (Automated)

Profile

Level 1 - Server

Description

Wireless networking is used when wired networks are unavailable.

Rationale

-IF- wireless is not to be used, wireless devices can be disabled to reduce the potential attack surface.

Impact

Many if not all laptop workstations and some desktop workstations will connect via wireless requiring these interfaces be enabled.

Audit Procedure

Command Line

Run the following script to verify no wireless interfaces are active on the system:

#!/usr/bin/env bash

{
  l_output="" l_output2=""
  module_chk()
  {
      # Check how module will be loaded
      l_loadable="$(modprobe -n -v "$l_mname")"
      if grep -Pq -- '^\h*install \\/bin\\/(true|false)' <<< "$l_loadable"; then
          l_output="$l_output\n - module: \"$l_mname\" is not loadable: \"$l_loadable\""
      else
          l_output2="$l_output2\n - module: \"$l_mname\" is loadable: \"$l_loadable\""
      fi
      # Check is the module currently loaded
      if ! lsmod | grep "$l_mname" > /dev/null 2>&1; then
          l_output="$l_output\n - module: \"$l_mname\" is not loaded"
      else
          l_output2="$l_output2\n - module: \"$l_mname\" is loaded"
      fi
      # Check if the module is deny listed
      if modprobe --showconfig | grep -Pq -- "^\h*blacklist\h+$l_mname\b"; then
          l_output="$l_output\n - module: \"$l_mname\" is deny listed in: \"$(grep -Pl -- \
"^\h*blacklist\h+$l_mname\b" /etc/modprobe.d/*)\""
      else
          l_output2="$l_output2\n - module: \"$l_mname\" is not deny listed"
      fi
  }
  if [ -n "$(find /sys/class/net/*/ -type d -name wireless)" ]; then
      l_dname=$(for driverdir in $(find /sys/class/net/*/ -type d -name wireless | xargs -0 dirname); do
basename "$(readlink -f "$driverdir"/device/driver/module)";done | sort -u)
      for l_mname in $l_dname; do
          module_chk
      done
  fi
  # Report results. If no failures output in l_output2, we pass
  if [ -z "$l_output2" ]; then
      echo -e "\n- Audit Result:\n  ** PASS **"
      if [ -z "$l_output" ]; then
          echo -e "\n - System has no wireless NICs installed"
      else
          echo -e "\n$l_output\n"
      fi
  else
      echo -e "\n- Audit Result:\n  ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n"
      [ -n "$l_output" ] && echo -e "\n- Correctly set:\n$l_output\n"
  fi
}

Expected Result

Audit Result: ** PASS ** - System has no wireless NICs installed, or all wireless modules are not loadable, not loaded, and deny listed.

Remediation

Command Line

Run the following command to disable any wireless interfaces:

# find /lib/modules/`uname -r`/kernel/drivers/net/wireless -name '*.ko' -printf 'install %f
/bin/false\nblacklist %f\n\n' | sed 's/\.ko//1' >> /etc/modprobe.d/blacklist-wireless.conf

Note: the *.conf file in /etc/modprobe.d/ in the above command can renamed as needed.

Default Value

Wireless interfaces are enabled if wireless hardware is present.

References

NIST SP 800-53 Rev. 5: CM-7

CIS Controls

Controls Version	Control	IG 2	IG 3
v8	4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software	x	x
v7	15.4 Disable Wireless Access on Devices if Not Required		x
v7	15.5 Limit Wireless Access on Client Devices		x