Detection rules › Sigma

WinRAR Execution in Non-Standard Folder

Status
test
Severity
medium
Log source
category process_creation, product windows
Author
Florian Roth (Nextron Systems), Tigzy
Source
github.com/SigmaHQ/sigma

Detects a suspicious WinRAR execution in a folder which is not the default installation folder

Known false positives

  • Legitimate use of WinRAR in a folder of a software that bundles WinRAR

MITRE ATT&CK coverage

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 1: Process creation

Rule body

title: WinRAR Execution in Non-Standard Folder
id: 4ede543c-e098-43d9-a28f-dd784a13132f
status: test
description: Detects a suspicious WinRAR execution in a folder which is not the default installation folder
references:
    - https://twitter.com/cyb3rops/status/1460978167628406785
author: Florian Roth (Nextron Systems), Tigzy
date: 2021-11-17
modified: 2025-07-16
tags:
    - attack.collection
    - attack.t1560.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith:
              - '\rar.exe'
              - '\winrar.exe'
        - Description:
              - 'Command line RAR'
              - 'WinRAR'
    filter_main_unrar:
        # Note: we filter unrar as it has the same description as the other utilities, and we're only interested in compression
        Image|endswith: '\UnRAR.exe'
    filter_main_path:
        Image|contains:
            - ':\Program Files (x86)\WinRAR\'
            - ':\Program Files\WinRAR\'
    filter_optional_temp:
        # Note: in some occasion installers were seen dropping "rar" in TEMP
        Image|contains: ':\Windows\Temp\'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Legitimate use of WinRAR in a folder of a software that bundles WinRAR
level: medium

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: selection

selection:
    - Image|endswith:
          - '\rar.exe'
          - '\winrar.exe'
    - Description:
          - 'Command line RAR'
          - 'WinRAR'

Stage 2: not filter_main_*

filter_main_unrar:
    Image|endswith: '\UnRAR.exe'
filter_main_path:
    Image|contains:
        - ':\Program Files (x86)\WinRAR\'
        - ':\Program Files\WinRAR\'

Stage 3: not filter_optional_temp

filter_optional_temp:
    Image|contains: ':\Windows\Temp\'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
Imageends_with\UnRAR.exeexcludes:Image field:"Image" value:"\UnRAR.exe"
Imagematch:\Program Files (x86)\WinRAR\excludes:Image field:"Image" value:":\Program Files (x86)\WinRAR\"
Imagematch:\Program Files\WinRAR\excludes:Image field:"Image" value:":\Program Files\WinRAR\"
Imagematch:\Windows\Temp\excludes:Image field:"Image" value:":\Windows\Temp\"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Descriptioneq
  • Command line RAR corpus 3 (sigma 3)
  • WinRAR
field:"Description" kind:eq
Imageends_with
  • \rar.exe corpus 5 (sigma 5)
  • \winrar.exe corpus 6 (sigma 6)
field:"Image" kind:ends_with