# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-DEB-SVC-021
title: Disable the autofs automounter
finding:
  title: The autofs automounter can mount file systems on demand
  description: Removable media or network shares get mounted whenever someone accesses a path.
status: active
profiles: [server, desktop-hardened]
risk:
  severity: medium
assessment: automated
tags: [services, autofs, removable-media]

description: |
  `autofs` mounts file systems (local devices, NFS or SMB shares) when a path under its maps is
  accessed, and unmounts them when idle.

  The control passes when `autofs.service` is masked or not installed at all.
rationale: |
  Automatic mounting of removable media lets anyone with physical access bring in files or
  malicious file system images; automatic network mounts reach shares that the administrator may
  not expect.
impact: |
  File systems listed in the autofs maps are no longer mounted on demand: mount them through
  `/etc/fstab` instead. Systems that rely on autofs, such as home directories on NFS, must exclude
  this control in their tailoring file.
notes: |
  The control is in the server profile and in the hardened desktop profile: on standard
  desktops, on-demand mounts are an expected feature.

audit:
  manual: |
    Run `systemctl is-enabled autofs.service`. It must print `masked`, or fail because the unit does
    not exist.
  checks:
    - id: autofs
      engine: systemd-unit
      description: autofs automounter.
      spec: { unit: autofs.service, state: masked }

remediation:
  manual: |
    Run `systemctl mask --now autofs.service`, or `apt purge autofs` if the package is not needed.
  effects:
    restart: none
    disruption: low
    lockout_risk: false
  rollback: |
    Run `systemctl unmask autofs.service` then `systemctl enable --now autofs.service`.
  scripts:
    - id: autofs
      from_check: autofs

references:
  - title: autofs(8), Debian manual pages
    url: https://manpages.debian.org/trixie/autofs/autofs.8.en.html
    publisher: Debian
    kind: vendor-doc
    accessed: 2026-10-18
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R62)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-18
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: R62
    relation: partial
    note: R62 asks to disable every unneeded service; this control covers autofs.
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-7
    relation: partial
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: MP-7
    relation: related
  - framework: cis-debian-12
    framework_version: "2.0.0"
    id: "2.1.1"
    relation: equivalent
  - framework: cis-debian-13
    framework_version: "1.1.0"
    id: "2.1.1"
    relation: equivalent
threats:
  - framework: mitre-attack
    id: T1091
  - framework: mitre-attack
    id: T1200

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["12"]
    environment: Proxmox VM, Debian 12 genericcloud image, kernel 6.1.0-54-cloud-amd64
    notes: "Fresh image passes; with autofs installed the check fails, fix masks, audit passes after reboot; tested with profiles server-hardened and desktop-hardened."
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["13"]
    environment: Proxmox VM, Debian 13 genericcloud image, kernel 6.12.113+deb13-cloud-amd64
    notes: "Fresh image passes; with autofs installed the check fails, fix masks, audit passes after reboot; tested with profiles server-hardened and desktop-hardened."
introduced_in: 0.1.0
created: 2026-10-18
updated: 2026-10-18