Audit file deletions and renames by users

Description

auditd rules in /etc/audit/rules.d/60-cirsec-delete.rules, key delete: unlink, unlinkat, rename, renameat, renameat2 and rmdir called by users who logged in, 64-bit and 32-bit programs.

Rationale

Deleting files is how an intruder removes tools and traces, and how data gets destroyed. The records keep the name of each deleted or renamed file and the user who did it.

Impact

Interactive users produce many delete records (editors save through a rename, builds remove temporary files). Size the audit logs accordingly.

Setting

Audit

1. Run auditctl -l as root. It must list the rules shown below (keys delete).
2. Run grep -h . /etc/audit/rules.d/*.rules. The same rules must be present, so they load at boot.

Expected rules, as auditctl -l prints them:

-a always,exit -F arch=b64 -S rename,rmdir,unlink,unlinkat,renameat,renameat2 -F auid>=1000 -F auid!=-1 -F key=delete
-a always,exit -F arch=b32 -S unlink,rename,rmdir,unlinkat,renameat,renameat2 -F auid>=1000 -F auid!=-1 -F key=delete

Automated: every check must pass. Scanners report each check by its id.

rules

Rules loaded in the kernel and present in /etc/audit/rules.d.

script: |
  command -v auditctl >/dev/null 2>&1 || { echo "auditctl not found: auditd is not installed"; exit 1; }
  want() {
  cat <<'RULES'
  -a always,exit -F arch=b64 -S rename,rmdir,unlink,unlinkat,renameat,renameat2 -F auid>=1000 -F auid!=-1 -F key=delete
  -a always,exit -F arch=b32 -S unlink,rename,rmdir,unlinkat,renameat,renameat2 -F auid>=1000 -F auid!=-1 -F key=delete
  RULES
  }
  loaded=$(auditctl -l 2>&1) || { echo "$loaded"; exit 3; }
  disk=$(cat /etc/audit/rules.d/*.rules 2>/dev/null)
  n=0 rc=0
  while IFS= read -r r; do
    [ -n "$r" ] || continue
    n=$((n + 1))
    printf '%s\n' "$loaded" | grep -Fxq -- "$r" || { echo "not loaded: $r"; rc=1; }
    printf '%s\n' "$disk" | grep -Fxq -- "$r" || { echo "not in /etc/audit/rules.d: $r"; rc=1; }
  done <<EOF
  $(want)
  EOF
  [ "$rc" = 1 ] || echo "$n rules loaded and present in /etc/audit/rules.d"
  exit "$rc"

Remediation

1. Write the expected rules to /etc/audit/rules.d/60-cirsec-delete.rules (mode 0640).
2. Run augenrules --load. If auditctl -s shows enabled 2, the configuration is locked: reboot to load the new rules.

Rollback

Delete /etc/audit/rules.d/60-cirsec-delete.rules and run augenrules --load (or reboot if the configuration is locked).

rules-file

command -v augenrules >/dev/null 2>&1 || { echo "auditd is not installed" >&2; exit 1; }
want() {
cat <<'RULES'
-a always,exit -F arch=b64 -S rename,rmdir,unlink,unlinkat,renameat,renameat2 -F auid>=1000 -F auid!=-1 -F key=delete
-a always,exit -F arch=b32 -S unlink,rename,rmdir,unlinkat,renameat,renameat2 -F auid>=1000 -F auid!=-1 -F key=delete
RULES
}
f=/etc/audit/rules.d/60-cirsec-delete.rules
t=$(mktemp)
{ echo '# Written by CIRSEC Baselines CB-DEB-AUDIT-023'; want; } >"$t"
if ! cmp -s "$t" "$f"; then
  cb_backup "$f"
  cat "$t" >"$f"
fi
rm -f "$t"
chmod 640 "$f"
if auditctl -s | grep -q '^enabled 2'; then
  echo "audit rules are locked (-e 2): reboot to load $f"
else
  augenrules --load >/dev/null
fi

Handwritten code reads parameters from CB_<NAME> environment variables. Each release turns these fixes into remediate.sh and an Ansible role per profile: dry run by default, a fix runs only when its check fails.

References

• audit.rules(7), Debian manual pages Debian, vendor-doc, accessed 2026-10-18
• auditctl(8), Debian manual pages Debian, vendor-doc, accessed 2026-10-18
• ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R73) ANSSI, guide, accessed 2026-10-18

Mappings

How this control relates to the other framework's: equivalent, stricter, looser, partial or related.

Threats mitigated

Related controls

• requires CB-DEB-AUDIT-011 Install and run the audit daemon
• related CB-DEB-AUDIT-029 Lock the audit configuration and load every valid rule

People and lifecycle