Rar Usage with Password and Compression Level

Status: test
Severity: high
Log source: category process_creation, product windows
Author: @ROxPinTeddy
Source: github.com/SigmaHQ/sigma

Detects the use of rar.exe, on the command line, to create an archive with password protection or with a specific compression level. This is pretty indicative of malicious actions.

Known false positives

Legitimate use of Winrar command line version
Other command line tools, that use these flags

MITRE ATT&CK coverage

Tactic	Techniques
Collection	`T1560.001` Archive Collected Data: Archive via Utility

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Rar Usage with Password and Compression Level
id: faa48cae-6b25-4f00-a094-08947fef582f
status: test
description: Detects the use of rar.exe, on the command line, to create an archive with password protection or with a specific compression level. This is pretty indicative of malicious actions.
references:
    - https://labs.sentinelone.com/the-anatomy-of-an-apt-attack-and-cobaltstrike-beacons-encoded-configuration/
    - https://ss64.com/bash/rar.html
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1560.001/T1560.001.md
author: '@ROxPinTeddy'
date: 2020-05-12
modified: 2022-03-16
tags:
    - attack.collection
    - attack.t1560.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_password:
        CommandLine|contains: ' -hp'
    selection_other:
        CommandLine|contains:
            - ' -m'
            - ' a '
    condition: selection_password and selection_other
falsepositives:
    - Legitimate use of Winrar command line version
    - Other command line tools, that use these flags
level: high

Stages and Predicates

Stage 0: `condition`

selection_password and selection_other

Stage 1: `selection_password`

selection_password:
    CommandLine|contains: ' -hp'

Stage 2: `selection_other`

selection_other:
    CommandLine|contains:
        - ' -m'
        - ' a '

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-hp` corpus 4 (sigma 4) `-m` corpus 3 (sigma 3) `a` corpus 4 (sigma 4)	`field:"CommandLine" kind:match`