Linux auditd: dd overwrites a file using /dev/null or /dev/zero

Flags dd command lines that overwrite files by sourcing data from /dev/null or /dev/zero.

FreeReviewedSigma · Low · v3

Product: linux
Service: auditd
Author: Jakob Weinzettl, oscd.community (SigmaHQ), DRL 1.1
Published: 2019-10-23
Updated: 2026-07-31

ATT&CK techniques

Impact

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
- T1485Data Destruction

What it detects

This rule flags Linux process executions where the dd command is invoked to read from /dev/null or /dev/zero, resulting in effectively wiping or deleting file contents. Attackers use this pattern to destroy data and disrupt incident investigation by overwriting target files with null or zero bytes. The detection relies on auditd telemetry capturing execve events and the dd invocation arguments that reference if=/dev/null or if=/dev/zero.

Reporting behind it

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Linux auditd: dd overwrites a file using /dev/null or /dev/zero

Pivot detection · T1485 · 9 related

Changelog

v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

linux-auditd-dd-overwrites-a-file-using-if-dev-null-or-if-dev-zero-37222991

title: "Linux auditd: dd overwrites a file using /dev/null or /dev/zero"
id: 04e79a91-d4b1-4d6f-b493-66cef4b8372f
status: stable
description: This rule flags Linux process executions where the dd command is invoked to read from /dev/null or /dev/zero, resulting in effectively wiping or deleting file contents. Attackers use this pattern to destroy data and disrupt incident investigation by overwriting target files with null or zero bytes. The detection relies on auditd telemetry capturing execve events and the dd invocation arguments that reference if=/dev/null or if=/dev/zero.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1485/T1485.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/auditd/execve/lnx_auditd_dd_delete_file.yml
author: Jakob Weinzettl, oscd.community, Huntrule Team
date: 2019-10-23
tags:
  - attack.impact
  - attack.t1485
logsource:
  product: linux
  service: auditd
detection:
  selection:
    type: EXECVE
    a0|contains: dd
    a1|contains:
      - if=/dev/null
      - if=/dev/zero
  condition: selection
falsepositives:
  - Appending null bytes to files.
  - Legitimate overwrite of files.
level: low
license: DRL-1.1
related:
  - id: 37222991-11e9-4b6d-8bdf-60fbe48f753e
    type: derived

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