Linux Wget Writing Files Under /tmp or /var/tmp

Alerts when wget creates files under /tmp or /var/tmp on Linux.

FreeReviewedSigma · Medium · v3

Product: linux
Category: file_event
Author: Joseliyo Sanchez, @Joseliyo_Jstnk (SigmaHQ), DRL 1.1
Published: 2023-06-02
Updated: 2026-07-31

ATT&CK techniques

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1105Ingress Tool Transfer
Exfiltration
Impact

What it detects

This rule matches process activity where wget is the executable and it writes/creates files with target paths starting in /tmp/ or /var/tmp/. Downloading into temporary directories is a common attacker technique for staging payloads before execution or exfiltration. It relies on Linux file event telemetry that includes the process image path/name and the destination TargetFilename.

Reporting behind it

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Linux Wget Writing Files Under /tmp or /var/tmp

Pivot detection · T1105 · 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-wget-writes-files-to-tmp-or-var-tmp-35a05c60

title: Linux Wget Writing Files Under /tmp or /var/tmp
id: 62bdd924-57ad-4c80-808d-ec7c60981208
status: test
description: This rule matches process activity where wget is the executable and it writes/creates files with target paths starting in /tmp/ or /var/tmp/. Downloading into temporary directories is a common attacker technique for staging payloads before execution or exfiltration. It relies on Linux file event telemetry that includes the process image path/name and the destination TargetFilename.
references:
  - https://blogs.jpcert.or.jp/en/2023/05/gobrat.html
  - https://jstnk9.github.io/jstnk9/research/GobRAT-Malware/
  - https://www.virustotal.com/gui/file/60bcd645450e4c846238cf0e7226dc40c84c96eba99f6b2cffcd0ab4a391c8b3/detection
  - https://www.virustotal.com/gui/file/3e44c807a25a56f4068b5b8186eee5002eed6f26d665a8b791c472ad154585d1/detection
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/file_event/file_event_lnx_wget_download_file_in_tmp_dir.yml
author: Joseliyo Sanchez, @Joseliyo_Jstnk, Huntrule Team
date: 2023-06-02
tags:
  - attack.command-and-control
  - attack.t1105
logsource:
  product: linux
  category: file_event
detection:
  selection:
    Image|endswith: /wget
    TargetFilename|startswith:
      - /tmp/
      - /var/tmp/
  condition: selection
falsepositives:
  - Legitimate downloads of files in the tmp folder.
level: medium
license: DRL-1.1
related:
  - id: 35a05c60-9012-49b6-a11f-6bab741c9f74
    type: derived

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