# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-DEB-PKG-010
title: Install only the packages the system needs
finding:
  title: Packages without a use on this system are installed
  description: Every unneeded package adds code that can be vulnerable, services that can be exposed and updates to follow.
status: active
profiles: [core]
risk:
  severity: low
assessment: manual
tags: [packages, minimal-install]

description: |
  A minimal installation contains only what the role of the system requires: no graphical
  environment on a server, no compiler or debugging tools on a production host, no tool installed
  "just in case". Debian makes it easier by letting the installer skip every task, and by tracking
  packages installed only as dependencies so that `apt-get autoremove` can remove them.
rationale: |
  Each package is attack surface: its vulnerabilities, its services and its setuid binaries.
  Compilers, debuggers and network tools also help an attacker who got a foothold. Fewer packages
  also mean fewer updates and a simpler review of the system.
impact: |
  Removing a package that an application relies on breaks it. Review before removing, and test on
  a non-production system first.

audit:
  manual: |
    1. List the packages installed on purpose with `apt-mark showmanual`, and check that each one
       is needed by the role of the system.
    2. Run `apt-get -s autoremove`: it lists dependencies that are no longer needed.
    3. Look for packages that rarely belong on a server: graphical environment
       (`dpkg -l 'xserver-xorg*' 'gnome*' 'kde*'`), compilers and build tools
       (`gcc`, `make`, `build-essential`), debuggers (`gdb`, `strace`), network tools (`nmap`,
       `netcat*`, `tcpdump`), unused interpreters.
    4. Check that `apt-config dump APT::Install-Recommends` matches the policy of the organisation.
remediation:
  manual: |
    1. Remove each unneeded package with `apt-get purge <package>`, after checking with
       `apt-get -s purge <package>` what else would be removed.
    2. Run `apt-get autoremove --purge` to remove the dependencies left behind.
    3. For new systems, start from a minimal installation (no task selected in the installer, or a
       minimal cloud image) and add packages for the role only.
    4. Write down the list of packages expected for each role, so drifts can be spotted.

references:
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R58)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-18
  - title: apt-mark(8), Debian manual pages
    url: https://manpages.debian.org/trixie/apt/apt-mark.8.en.html
    publisher: Debian
    kind: vendor-doc
    accessed: 2026-10-18
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: R58
    relation: equivalent
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-7
    relation: related
related_controls:
  - id: CB-DEB-PKG-011
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
introduced_in: 0.1.0
created: 2026-10-18
updated: 2026-10-18